Sounds like an episode of Rosemary and Thyme
It really depends on what you are willing to do yourself. If you're happy to allow someone to steal from you and brush it under the carpet, then do just that. This is absolutely what the thief is banking on you doing.
If it was me I'd ring the gardai. Then ring everyone who was in your house and let them know a theft has occurred in your home. Let them know the gardai are now involved and you are looking for all names and addresses as the gardai have requested them and they will be in contact. You could mention that if the money is returned/dropped through your letterbox within the next 24 hours you will drop the case. Alternatively let the gardai do their job.