How can I increase the resolution of a mobile clip?
Unfortunately, no. Increasing the resolution of a video after recording is impossible. You can upscale the video, but that will simply copy the pixels and maybe interpolate a bit, but the result won't look any better than the original. If, as I presume, whatever you saw there is just a bunch of colored pixels in your video, there's nothing you can do to change that.

Whatever you saw there, maybe it was just not meant to be caught on tape ...