That's been my experience with pepper plant seedlings exposed to temps below 45F.

Yeah, give up on them or have very few this season

Not to second guess boulderbelt who always has good advice, but i've never had this problem. The temps in my greenhouse regularly dip below 45F in late winter when my peppers are still in flats and I have great fruit sets regardless.
Frost nipped plants may be another level of extreme, and i can't say from experience if they'll recover. Good luck.
-Mark

Haven't had that issue myself, but perhaps it has something to do with duration of uninterrupted exposure as well. I plant mine out in early June when average lows are in the upper 40s and we get mid-40s occasionally throughout the summer.

Thanks for the input. Doing a bit more research online shows the jury is still out, with the effect noted but dependent on air temperature, soil temperature, duration of event, and plant variety. I guess nobody has done a direct study to test all the variables. I've started another flat of the same varieties and they will be under grow lights indoors until it is much warmer out. In the meantime I have moved the afflicted flat inside as well. They appear to have recovered nicely and are growing on well. I'll try planting them out side by side and see if there is a difference.