If You have completed the sale or activated the ticket and You feel like something might have been wrong then You can always check the transactions from the "Finances" menu.

In order to do that please click "Exit cashier" on the top:

Then the right place opens ("Finances" -- "Sale transactions") where all the transactions are displayed:

If the needed transaction is not in the table then it didn't happen properly. 

Additional: What can I do if I make a mistake in using cashier system?

Where can I see the history of sold services?