It depends on your rules, if your solely basing it on TDA rules then yes, he can retract and re-consider his actions. My rules require the the button player to leave in the 1,500 as he was not paying attention, to penalise him further (by making him put in 15,600) is not in the best interests of the tournament and fairness IMO - he said "raise 1,100" not "raise to 1,100" or "raise to 1,100 total" so it's 400+1,100. In my book he can then either a) call the 8,000 total or b) fold, leaving the 1,500 in the middle.
Regards
Stuart