I copied these TGIDs from the old system a long time ago and converted (divided by 16).
I don't know if they are still good.
1943 TPD Util 8K
1945 TPD SID 7N
1947 TPD MVal Tac 7F
1949 TPD Util 8L
1951 TPD Records 7K
1953 TPD Gilcr 7A
1955 TPD St Cr 1 7O
1957 TPD Rside Tac 7I
If you find more active unidentified talkgroups there is a wiki article for them.
Seeing an ID "Pop Up" vs hearing audio on it is a big difference, encrypted ID's will Pop Up and then disappear as the (Uniden) radio is going to skip encrypted traffic. Looking at my old TPD Files from 2014, nd5y is correct and that 31120 is/was TPD 7N SID.