If you wet sand the run it will not make it glossy but it will not match the rest of the piece. If you buff it after sanding it will be glossier than it would be if you just painted it.
99% of the time, if I have to sand a flaw in a semi gloss/flat color I sand and re-shoot it. Little dust nibs can be carefully sanded out with out anyone noticing (there is the 1%) but runs are going to stand out.