I think that hotels don't contact guests about left items because they could well belong to a previous guest. If someone rang to ask if you had left a valuable item, some people would probably just say yes and take something that wasn't theirs.

I once left a jacket at Portsmouth (UK) Marriott. I called immediately when I realised I had left it and an on the ball housekeeper found it within 10 minutes and posted it to me at no charge. I had it back in two days. Excellent customer service. If the hotel had identified the next guest as the owner, they could have accepted an expensive item of clothing as their own only to have me call a week later to find that had happened ....