he may be right, it may be too late...hard to say
It might have been the fertilizers you gave it.
After such a shock, its best to wait to give most any plant fertilizers, give a plant a good 2 weeks after such a shock before you give it fertilizers, plus water it daily (sandy soil, 2 times a day) for 2 weeks, then water it 2 times a week for the next few months... then every week for about 6 months or more.
Also, take great care in handling roots, don't wash them off unless there is dire need to do so, and be sure not to break any roots.
IF there is no help but to break a few roots (real bad idea) or you simply must wash the roots... or if it seems the plant should have more roots (maybe they were broken or stunted before you got it) then I like to sprinkle Vermiculite directly on the roots before putting it in the ground.
Keep in mind that I'm really just an amature gardener, but I've grown a few plants that everyone said were going to die and are not quite healthy... I even cloned an eggplant lol...
I never knew you could do that with those
Also if anything I said here is just plain wrong, please correct me... I'm always learning