I lost mine the same way.

On Sunday. Was going north on 275 from St. Pete and got to the MLK exit before the HF Bridge and some dude drove up next to me. Grabbed his cellphone, pointed to me, pointed to cellphone, pointed "back there".

After I realized what he was trying to say, all I could do was in my helmet to myself.

I usually keep it in my jacket pocket and zip it up, but I guess I must of had a brainfart and just forgot to zip it up.