Legal Question in Criminal Law in Florida

I'm not quite sure what you mean. Accidentally losing something is generally not enough to rise to the level of theft. But if you were "borrowing" someone else's money and then lost it, yes you could be charged with theft. Taking or using money that belongs to another person, even temporarily, is theft.

If someone gave you money to buy illegal drugs, then you could still be charged with theft if you keep the money, but its questionable whether the aggrieved party would actually call the police.