With my mash cooler, the temp only drops a degree or two over the course of an hour. Your equipment may differ.
There are several factors that can cause a high FG, and mash temp is one of them. But since yours is only a partial mash, and the temp wasn't too terribly high, I doubt you'll see much of a problem. Just aerate well and pitch a big starter, you'll be fine.
My one stuck fermentation, in an early all-grain batch, was a stout that finished at 1.032. I traced the problem to a bogus digital thermometer that read 8 to 10 degrees low - so I mashed in the low 160's. It was still beer, people liked it.