Don't email them write to them.
Write directly to the hotel manager setting out the facts, who you spoke to and when etc and ask him to reply within x about what they intend to do.
Ordinarily I think you don't have a leg to stand on, I could say I lost a �2000000 ring there and it could be a lie however, as they have admitted they did have it the onus is now on them.
If they sent anything by post it is up to them to chase with the post office (they have the contract with post not you) as untill you get it it is still the hotels responsibility.