I get 5,840 for highlit. Highlighted gets 27,100,000.

I think Pinker's point was that verbs with recently derived meanings, e.g. a batter flying out, and newly built verbs, e.g. highlight, are regular even if the root verb is irregular.

AHD lists only the regular past:

http://www.bartleby.com/61/70/H0197000.html