Pantech Impact back won't fit properly

[xElyon]

I've had my Impact for almost two years now and I love it, but there's one problem I've had recently. It's usually a strong phone; it's flown out of my hand across a room into a wall and onto the floor, but a few days ago I dropped it onto a tile floor from about a foot and a half off the ground and the back came off, and now it doesn't fit anymore. I've had to put packing tape on it to keep it from falling off. None of the little plastic tab things have come off, and there's nothing blocking the slots they're supposed to fit into, and nothing's bent, so I can't figure out why the back doesn't fit on.