Yeh, normally have cards, or coins with me - Or two elastic bands on my wrist or there's my reserve bands on my other wrist, my ankle, and in my wallet (just in case!)
But with absolutely nothing!!
Erm... see what i can borrow first, (wow - can I borrow that rather ordinary looking pack of cards...thanks... - what's that? Svengali! no is that a type of brand? - never heard of it...hehehee

)
Then, mental card forces...or invisble deal - ala Derren Brown.
Or, that one, where you wind their fingers in together (it kinda works).
If kids...thumb stretching trick...
After that, yeh, i leg it!!