Yea, that was one of the "bad" surprises when I bought mine. I was totally surprised that there were
no bottom-of-the-plate fasteners on the tailgate!
What I have been looking for, are 1/2" long, round, rubber bumpers that would "snap" into the licence plate's bottom holes from the back. As of yet, I haven't found any. I know I have seen these somewhere, but just can't remember where.
I also have seen, posted somewhere, someone documenting that some Escapes came with small rubber bumpers attached (glued) onto the tailgate itself, and some don't, all of the same model year. This person actually went to a Ford dealer, and snapped some pictures to document the difference.