since you aren't sure that the fish truck misled you (they may actually HAVE given you RES) then the GSF may have come from another local water source. If the GSH came in on their own, you could have LMB as well? If so then adding more could produce that dreaded Male plus Female LMB equals unlimited LMB that others are struggling with.

You may want to set some fine mesh 'make them yourself' fish traps and see what you can sample from your pond. The older RES stay deep and do not easily go in traps but the younger RES easily enter traps. If you get red ear tabs you know the fish truck gave you at least a few of the advertised RES that you paid for.

You may want to fish with a 2-3" GSF under a float and see if any other LMB exist in your pond already. If you already have LMB then the equation changes again and the balance shifts.