As far as I can tell the rules are very vague on if items are discarded on use. The rules for magical friends and spells however are very clear and specifically say discarded on use. The reason I have doubt (and this question) is because I've encountered several items (ironically?) that save items and have yet to encounter anything that makes you discard an item.
https://boardgamegeek.com/thread/1705755/rules-problemsclarifications does denote that in order to remove an item you have to discard it, which I can see from the rules now that I read this, but wonder if I'm just biased by this opinion. It would at least make an application for "saving" items however.
That entire thread above just seems to be users answering other users questions, which is great but hoping for a more official source if one exists.