From KS4ED

[KS4ED]

This may have been mentioned before but worth suggesting again if
it has...seal the deal with a phone call. Get a "hard line" phone number,
be cautious of "I only have a cell phone..." and try and have a little chit-
chat conversation with the seller / buyer about Ham Radio.
The price of the long distance call may be well worth the cost later.
Deal with Hams only...as Scott suggests.
If it appears you are about to be be ripped off use the search of QRZ.com
putting in the dead beats name and or street name or road and or zip code.
Pull up his location on Map Quest, write down as many of the streets and
major roads around his posted address you can. Look them up on QRZ.
The LID just might live on the same road or street of another Ham who
just might be able to help you. Be creative in your investigation.