An arboreal frog digging in deep in the substrate is usually a warning signal. I've heard people especially having this problem when the humidity is messed up (often to low levels). Could also be because it's too hot, since the digging occurred at the colder side and it's likely that it's cooler at the floor than the top (if you have a light on the top).
Could also be that the frog is just adjusting to the new environment, since you did stir a few things up, so monitor it and give it a day or two, see if it climbs up from that fox hole.
Also:This is also a habit that you might want to reconsider. It's never good for the frog. Best case scenario (although stress is very hard to not cause), nothing happens. Worst case, everything else happens.Average handling once a day for a short time while I do poo checks (she usually sits on my shoulder)