i once picked up a hitchhiker who claimed to be a marine trying to get back to portsmouth/ plymouth/ somewhere south of me... i was in uniform and he happily started telling me about his job etc (some sort of boarding operations blah) bit weird. he said he claimed to be rn because if he wrote marine on his bit of cardboard no-one had picked him up... he'd had his jacket stolen in a bar with his phone and wallet which had his id card in etc so he was hitching back to work to get an advance of pay etc. he'd got a bloody great bergen. he borrowed my mobile to call the guardroom as he'd spoken to someone or other earlier to let them know.
i didn't tell him my name or dh's name, just mentioned dh was army. he said his cousin was in the reme, but i probably wouldn't know him. told me his name. i said, blimey, i went to his wedding. and dh and i are godparents to their kids. he said he'd missed the wedding because he was in
so i dropped him off at reading services (it was about 4am at this point) and gave him £20 to get some breakfast (he'd been hitching since 10 the previous morning working his way south and hadn't eaten) - told him to give it to his cousin next time he saw him/ send him a cheque.
finished driving home. went to bed. got up the next day and mentioned to dh this weird coincidence. got bollocked for picking up a hitcher etc etc.
saw the friend a month or so later as he brought the family over for sunday lunch. said to him 'oo, have your seen your cousin? did he tell you i gave him a lift, weird eh?' and he looked at me completely blankly. no cousin.
then it clicked. he'd picked up a hitcher. gave him some money for food. and then gave him his business card because it had his work address on, not his home one, and said to the bloke 'send me a cheque when you get sorted, or i'll know you were just a con man'. no cheque.
so there's this weird little chap with lots of war stories hitching round the south of england getting money/ fed by military drivers (who apparently are the only people that pick up hitchers).
apparently they've had to publish on pt 1 orders across the region to be on the lookout for a male hitcher with a bergen (!) who claims to be a marine who's had his wallet nicked and to have lots of warry vessel-boarding stories.... none of the names he has given have been traceable. 
there are all sorts of people who for some reason really really want to be military (esp with sf connotations). i have no idea whether your chap was legit or not - but there are some odd folk about. 
and i'm not allowed to pick up hitchers any more. 
our mate was mortified that this geezer is now using his name to embellish his stories. he must have literally hundreds of business cards that he's memorised though. how clever is that?