And yes, there is a small screw in the side of the bumper cover that is colored black with a marker.
There are some screw holes along the splash guard. If those have the holes ripped open, that is another matter. This part will obviously not help you re-attach the splash guard.
The wheel was off for a totally unrelated matter. You do not need to take off the tire to do this fix. It is convenient to have the splash guard at least partially removed though.