Well, you might have your information slightly incorrect.
If this was a phone call, it was made via a phone patch over a repeater. This makes this a grey area, because if you look at the law that way, every ham radio operator that monitors a phone call made by another ham via a phone patch would be in violation of the law.
The repeater site for the MED channel is for radio communications, even though it has a phone patch capability.
The best thing to do is just don't tell anyone about the conversation that took place, as has been mention by others.
Not illegal. ECPA'86 which made cell phone monitoring illegal is radio service specific, not frequency specific. If it was a phone patch made on a med channel by medical personnel on their radio system (a Part 90 service), it's not illegal to monitor, and it's emergency services communicatons, which are exempted in the "it shall not be unlawful" clause in ECPA'86. As other have mentioned, don't divulge or use what you hear for any type of personal gain (prohibited by Section 705(a) of the Communications Act of 1934).
Do you (the OP) live in a densely populated neigborhood like in an apartment or condo complex? If so, you may have heard a spurious signal from a 900MHz residential cordless at HALF the transmit frequency. The transmitter in the phone (handset or base unit) multiplies a lower frequency up several times to get the final transmit frequency in the 900MHz range. Some of the energy in the multiplier chain in the transmitter leaks out but is supposed to be under limits set in Part 15 of FCC rules and regs. The phone may have a real "dirty" transmitter and strongly radiating spurious signals all over the spectrum in addition the intended final transmit frequency. OTOH, it could be a transmitter that's clean and fully FCC-legal but you just happen to be close enough to hear what little energy does leak out. If it's from a 900MHz residential cordless phone, the source is likely VERY close to you, like within about 100ft or less.
UHF freq 463.175MHz---> try listening at 926.35MHz (463.175 x 2) to see if this is what you're hearing. I live in an apt complex and I hear this crap from time to time in the 462MHz range on the GMRS/FRS freqs. In my situation it's usually coming from the apartment either immediately next door or across the hall from me.
Keep in mind that it is illegal to monitor residential cordless phone transmissions (crazy!) however ECPA'86 has a clause in which states that it's LEGAL to monitor when you're a victim of interference from a "prohibited" transmission to the extent necessary to identify such interference. After you've identified the source, you must stop listening according to the law (crazy, unenforceable..unconstitutional?..don't get me started on this one). IMHO, the whole thing is a farce to begin with (and likely unconstitutional), crafted by Congress to help the cell phone industry perpetuate commecially-serving lies about privacy. However this is straying OT...
All legal issues aside, I suspect what the OP heard was spurious signal(s) from a 900MHz cordless phone operating nearby.
Good luck and don't listen to anything that I wouldn't listen to (go figure). <wink>
