Fly in garden pot?

When I was out watering one of my containers earlier I noticed an insect coming up almost to the top of the compost. I fished it out with a plant label praying it wasn't a vine weevil, thank goodness it wasn't. It looked like a brown fly but didn't seem to be able to fly (maybe because I'd watered it!). The container has a Dahlia top mix tuber planted in it that I recently bought in Wilkos and fresh compost. Unfortunately I didn't manage to get a photo. Any ideas of what this could be?