The only problem I see with this scenario is bringing Cowser back up could possibly affect his rookie status and service time. If he did well his first time up and was sent back simply due to a roster crunch, then fine. But why do so when he hasn't demonstrated he belongs in the majors?
Yes, he scuffled during his first call up, but a .316 / .442 / .526 slash line in AAA does in fact demonstrate he belongs in the majors.
The question is roster spot availability.
It sucks, cuz yeah, Adam Frazier should not be playing LF.