/cgi.ebay.co.uk/1-x-Purple-striped-Apple-snail-15mm-/250612003827?cmd=ViewItem&pt=UK_Pet_Supplies_Fish&hash=item3a59a3b3f3
and it takes many water changes to get rid of the smell too.
maybe he's just settling in as you say, just keep an eye that the inactivity doesn't go on for too long or the snail doesn't stay in the same place all the time.