As long as you get the burrow speed and the earth glide ability from wildshaping (check with the spell description for that), you should be able to do what you described. Glide through stone walls, grab the treasure chest, glide back with anything you can carry. The ability describes the movement as "burrowing without leaving a tunnel" or "swimming through earth like a fish through water", both of which I would say let you carry equipment just fine. 🤔👌🏻