I would just keep trying. Of course this won't work in every situation, but so far with my broodies it does take a day or two approximately for them to adopt the chicks. I put them in at night and check several times during the day, being sure to put the chicks right back under mom after I encourage the chicks to eat and drink for a few minutes -- even if the mom seems to eye them suspiciously, make noise, or peck at them. So far they seem safer under mom so I try to keep them under her as much as possible. If she's truly broody, she won't get up much if at all. Don't give up! In a couple of days, she'll snap out of it and start foraging around with them. Never going back to a lamp if I can help it! Love my Buffs!!
P.S. I don't use fake eggs, either. My broodies get broody on nothing (literally, just an empty nest) and I pop chicks in there without any deception necessary. I don't think it matters if there's real eggs, fake eggs, or unicorn poop. It's all hormones and temperatures and warm fluffy marshmallows making cheeping noises (or something like that!).

Also, I don't do a broody box or anything. They nest wherever, even out in the open, and we've had no trouble. That being said, I tend to only keep more docile breeds. Right now we have buff orpington, delaware, ameraucana, easter egger, cochin, and one lonely new hampshire red (probably the most aggressive breed in the hennitentary at the mo').