This missing euro brain teaser is really mind boggling

Right look it’s not a new puzzle but every now and then this brain teaser rears its ugly head and wreaks havoc.

It's been doing the rounds on the internet thanks to The Lad Bible. We’ll just jump straight in because this is a mind fuck and any unnecessary words will only add mores confusion. Basically it goes:

Three lads check into a hotel, asking for one room for the night. The clerk says the room is €30 so the chaps had over an even €10 each. Later the clerk realises that he's overcharged the lads and the bill should only be €25. He takes €5 to refund to the lads and heads to their room to return it. On the way he realizes that €5 will not divide equally amongst three. The clerk decides to keep €2 for himself and refund the chaps a euro each. So, each of the lads got €1 back: meaning they only paid €9 each; bringing the total paid to €27. The clerk has the leftover €2. That’s €27 that lads paid, plus the €2 the clerk kept = €29 So, if the guests originally handed over €30, what happened to the remaining €1?

Enjoy. Bye. (Sorry).