About 10 years ago now, I'd just moved into a nice high-rise apartment in downtown Detroit next to Joe Louis Arena, and was listening to the scanner while unpacking some boxes on a Saturday night.
At the time, Detroit PD dispatch & some other ops was on the 453MHz analog system, while some DPD special units were on Detroit's 800MHz analog trunked system.
The scanner stopped & I heard "Hello? Hello? Is this thing working? Can anyone hear me?" I looked at the freq, & it turned out it was an 800MHz talkgroup that I had ID'ed as being DPD's 3rd or 4th precinct Special Operations Section or Investigative Operations Section.
SOS was a precinct-level detail that'd drive around in unmarked cars with usually plainclothes officers (30-series units on the patrol dispatch channel, nicknames on their 800MHz talk group) & handle minor vice, narcotics, selective enforcement stuff, etc. that wasn't major enough to be handled at a Group or Division level. IOS was similar, except they were detectives that'd mostly do crime follow-up investigations.
Anyway, for the next 30 minutes, this white male keeps keying up frequently on the same talk group, asking no one in particular if his radio is working, can anyone hear him, etc. He even gave instructions on how to key up a radio & respond to him. It was getting pretty annoying, yet I didn't want to lock out the talk group.
Finally, he says "Hey, if you can hear me, give me a call at 596-####." I knew 313/596 was the PBX for most Detroit PD facilities, so I assumed this knucklehead really was a DPD cop & not just some fool that found a radio, and I decided to do this guy & myself a favor & call him up & tell him his radio was working, so hopefully he'd stop making all the stupid transmissions on the talk group.
I called the # from my home phone, the guy I heard on the radio answered the line, and I just said something along the lines of "Your radio is working fine. I've been hearing your stupid transmissions loud & clear for about the past 45 minutes."
He immediately responds with "Look, that radio you stole cost the PD $2000 and you'd better give it back or else I'm going to be in big trouble. Just return the radio & we won't arrest you!"
My "OH $HIT!" reaction was to hang up the phone. I immediately figured out what was going on -- the SOS must have temporarily detained some dirtbag in their car (their cars didn't have cages) or in their office, they let the guy go, and then they noticed one of their 800MHz STX radios missing, and they were trying to lure the thief into responding on the air with all their transmissions.
The guy gets on the talk group & again repeats that they just want the radio back, and "you better not make us come find you!" & then periodically makes other transmissions along those same lines.
Meanwhile, I'm thinking that if they really went all-out, they could trace the phone call I made directly back to my new home. Not a huge deal, since they'd then see I wasn't the dirtbag that took the radio & I could just tell them the truth.
However, if instead of just knocking on the door, they were able to get a search warrant & kicked-in the door while I was home, my small young dog may very well have run up aggressively to them, and they might shoot him. If they shot my dog, I knew very well that I would absolutely try to kill whatever officer(s) shot my dog (living in downtown Detroit, I had numerous firearms immediately available), and the situation would obviously be very ugly.
I considered calling the # again & telling the officer the truth -- that I'd simply been hearing him coming thru my scanner & thought I'd do him a favor by calling the # he gave & letting him know the radio was working, but I was also aware from hearing prior conversations on that & similar DPD talk-groups that the morons thought those trunked 800MHz were completely secure, so he wouldn't believe the scanner bit.
I didn't call, and for the next couple days & nights I was a little nervous, but nothing ever ended up happening. I dunno if they ever did find the radio or not.
But a couple weeks later, I did call that same # again & someone answered by saying "#3 SOS," so I was able to ID who used that talk group!
About a year later, I'd made some friendships with DPD Special Response Team & Communications Operations Section command staff, even almost helping them track down a stolen 453MHz DPD radio but the battery on it died before they could sort out the red tape for me to help.
I told them the story above (minus the part about how I'd shoot back if DPD had done a raid & shot my dog...) & they found the situation to be absolutely hilarious.
"No good deed goes unpunished!"