I've found abandoned credits before (small amounts) and printed the TITO..

I then just insert that ticket into a machine I'm playing and use the credit.

I've also found larger amounts (up to $5 or so).. I sit at the machine for a while and if no one returns, I just play the credits or I just cash out the credits and insert it into a different machine I'm playing..

Sometimes I just take them to a redemption machine .. but I never take them to a cashier.

On one of our bus trips, someone cashed out credits on a machine and was caught by security.. they were told the abandoned credits were property of the casino.

I haven't had a problem so far, but I guess I could be tapped on the shoulder by security in the future..!