What are the chances? money/cash related?

I was just paid $180. but I didn't count the money. But I know there was a receipt on top (saying how much they paid me)> i just put it in my wallet. When I got in my car, I counted it. It looked like I was $50 short. The money looked like this: their receipt, 4x20, 1x50. Then there was another receipt under, for gas, which I had put in days ago! So I'm missing $50!

but the thing is, I have a 50 in my wallet. But it's quite far from the money I just received. under that gas receipt, there were 2x$20, and then the $50 was under that. so i'm pretty sure it was there all along. what are the chances that i really received the full $180 but one of the 50s got put behind another thin, small receipt & 2 used 20s? when i put in money, i grab it firmly, open my wallet & put it in the available space in the front. i find it hard to believe that a 50 could wedge itself in like that. none of the bills were crisp.

i'm pretty sure i'm missing a 50 from them. but how do i make them believe me?
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I don't think you can do anything now. But it won't happen in the future if you count it out in front of them and then smile and say thanks, that's perfect (or conversely, this doesn't seem correct). Now, it is the same sort of situation as going back into a shop after you have left and saying the change wasn't right. You simply can't prove it unless you checked it before you moved away from the till.

Look on it as a useful lesson. Take nothing for granted. It might have happened once, but it won't happen again. You are alert now.
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You can go in and ask the cashier to reconcile their cash drawer to see if it balances. They may or may not be able to do this. If they do and they balance, you are out of luck and they won't believe you. If they reconcile the cash drawer and it is over by $50, you'll get the money.

This is a lot of unnecessary hassle. You should always count the money in front of the cashier.
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you have a very large sounding wallet with multiple dimensions that money can sneak into