Just to clarify, did they fall out of the bag into the tank or onto the floor? If they fell into the tank it'll probably be least stressful if you just leave them in there and acclimatize the other fish on its own, rather than chasing them down, putting them back in the old water, then dumping them back in again.
My preferred method for acclimatizing fish is to use the drip method. Put the fish in a jar half-full of water (or less, just leave them a couple inches) and take a length of air tubing, either use a flow regulator (little valve with a knob, costs maybe a dollar) or just tie a knot in the hose to keep the flow at only a couple drips per second. You may have to tie several knots to get it down to the rate you want it at. Let the jar fill up, then drain the water down to the level you started at and repeat. Get rid of the water you drained out, you don't want to cross-contaminate your tank. Do this about 2 or 3 times, after a while all the water you started with will have been drained out and your fish will have become very gradually acclimatized to your water's parameters. I used this method when introducing 7 sparkling gouramis into my tank, the entire process took about 6 hours (I was being extremely paranoid about shocking them since the store tank had a PH in the low sixes and mine was in the high eights) but I didn't lose a single fish.