Go up a level as an item

[killshot111]

This is probably a dumb question but I'll let the moderator flame me if it is.

I was playing a game where someone was level 9 and as treasure, got a couple "Go Up A Level" cards. Since he couldn't use them (was lvl 9 after all), he played it in front like an item and "carried" the "item".

I wasn't sure that was legal since I don't think these cards are considered items (no gp value, no "Usable only once" on the card, etc.). However, most if not all treasure cards are items. He was "carrying" the cards b/c he had more than 5 cards in his hand and didn't want to give any away and wanted to keep them for safe keeping in case he COULD use it at a later time.

Is this a legal use of these cards/treasures? Can he "carry" these cards like items to save for later when he CAN use them? Thanks in advance for your reply.