It's an unfortunate reality. You can't really trust anyone in the world these days, and it's really disappointing. Especially when people take it to the extent that they'd steal a few pixels on a game.
It's true, people get so consumed by pixels that it affects how they act. For this exact reason I think Jagex introduced lending, so you could borrow items and the lender would have peace of mind that he would get his items back after a specific time period.
Unfortunately, it seems like you can't trust a godamned person on Runescape these days. Even your so called "friends" will be quick to scam you or screw you over if the chance arises.
I do have 1 person I trust fully in Runescape, and sadly, the ONLY reason is because I know him in real life and he could never just scam me or pull something like that as I would show up at his door 15 minutes later.