Strange. ?Are you sure you had the shift lever in D or 3?
My last 4L60E used to throw fits and go into "limp home" mode way too often. ?Basically that was going straight for second gear and staying there. ?
Did yours up and downshift properly from there? ?If it was in trouble-mode, I believe the computer has to be reset, and you'd almost definitely see a code thrown. (Service Engine Soon light).
If it worked okay, did you maybe catch what the speedometer was doing? ?Maybe it's possible that the speed sensor hicuped and caused the tranny to grab second too early?
Happen to have access to a OBDII scanner?