I was not able to verify the authenticity of the above photo of a check from Hunter S. Thompson. However, it sure sounds like something he would do.
Bart tells a Buzzy story about the time that he worked at Maryland Bank and Trust. Bart worked in the back office room along with several others who did things like sort cancelled checks, record deposits etc.. A young lady responsible for sorting thru deposited checks noticed one from Bart to Buzzy’s for $20. In the lower left hand corner of the check in the For section, Buzzy had inscribed what the check was for. The lady began laughing and asked Bart across the room, “Hey Bart, what where you doing writing Buzzy’s a $20 check for prophylactics?”
A quote by Hunter Thompson in his Wikipedia bio “I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they’ve always worked for me” reminded me of something Johnny Ford once said. 
Johnny had just come into the Store and after I’d asked him how he was doing he said “This cop stopped me as I was driving down here and asked if I had any alcohol, firearms or drugs in the car. I told him I was pretty sure that I didn’t have any alcohol or firearms but I thought I had some drugs in there somewhere that I couldn’t find. I told him I’d sure appreciate it if he could find them for me.”
You know, now that I think about it, Johnny and Hunter had quite alot in common didn’t they?!)