Probably just slipped their mind, but how nice of them to acknowledge that you sent something back and to pay you for the postage!
I kept things found in the room and waited to hear from the guest, unless I knew that there would probably not be a problem emailing them to let them know they left something behind. Have had things left after "flings" and didn't contact the guests....those items went to the donation box, if appropriate.
Had a gentleman leave some clothing when he stayed here & contacted him and offered to return it and would charge his credit card for the postage. He said that he would send a postage paid mailer. I guess he thought that I'd charge him a whole lot more than it cost to return the item?? The pre-paid mailer worked out well. After that, that's the direction I took for most people with larger items. Send me a mailer and I'll return your item.
I had a lady leave a small jewelry case here and FINALLY got the daughter (who had booked the rooms for her parents) to respond to my repeated emails with an address to send it to. I don't think the jewelry was that expensive but I sent it insured & delivery confirmation, which I received. Never heard back from the mother that she received it, even after enclosing a note thanks for your stay & to please email me that it arrived safely. Didn't receive payment for the mailing either. This made me change my procedure to get addresses on everyone in our rooms, even when booked by someone else staying here.
A guest lost a necklace somewhere here in town that had sentimental value & I felt so bad for her! Probably lost it while walking around and taking photos. :-(
Our guest registration form (which is generated by the rez system) had a note that read something like "XYZ Inn not responsible for lost or stolen items"...taken right from some hotel registration form.
A guest that takes the time to send back the postage, no matter when, is a nice guest!!