Take it easy I can understand how this irriates you because I have the same experience with you.
If I were you I will contact that 師父 even though recommended by your 佬個姐夫 because this is your right, simply tell him in a nice tone and tell him that you will be available anytime for him to fix it.
Have you got spare tiles with you, if yes you may even tell that 師父 that material is ready for him, otherwise you can call up the store that you purchased the tile and ask them to check stock for you (provided you still got the invoice and model number).
If that 師父 refuse to fix it for you all you could do is ask someone to fix it for you. Not to difficult, all you need to do is to remove the one on top of that hallow place (indeed break it); fill the hole up with cement than put a new piece of tile back.
It is all depend on the 手工 and whether the 師父 remove the old tile nicely (without breaking too much surroundings and able to remove the cement underneath). I believe he should know how to do it nicely just that if he willing to spend a little bit more time to fix it for you.
Mine is totally ok because I was at home to monitor him. Try calling the supplier and see if they have stock for your tile.