It did take on a new meaning, then lose that meaning. I'm not sure how best to characterize that meaning, but I do have evidence it existed. From the Oxford English Dictionary:
âb.b Of troops: Properly disciplined. Obs. rareâ"1.
ÂÂÂ1690 Lond. Gaz. No. 2568/3 We hear likewise that the French are in a great Allarm in Dauphine and Bresse, not having at present 1500 Men of regulated Troops on that side.
(Yes, Slashdot will probably have munged a few of those characters. It's a copy + paste from the electronic edition.)
At any rate, I disagree that it's strange for a word to gain a new meaning and lose that new meaning. It doesn't require extraordinary evidence because it's simply not that unusual. Note however that the word never lost its old meaning, so it didn't "revert"; it merely lost the new meaning.