Fumble recoveries after the whistle do count. The continuing action after the whistle doesn't count (like if the player recovers and then scores, the score doesn't count).
The rule is no different than a fumble (a backward pass is a fumble). And the Panthers have gotten the ball after replay plenty of times when a player was whistled down yet it was ruled a fumble later.
Players are taught to take possession of the ball on these plays. You could even hear the running backs coach yelling at the receiver for not picking it up.
Huh? It was clearly a backward pass. If anything the refs screwed the Pats by blowing the whistle costing them a TD. I haven't seen an official blow the whistle that quick on such a close play in quite a while.
The Panthers have benefited from that stupid rule a million times. The only thing the whistle does it keep the continuing action from counting. That is why most officials don't blow their whistle on these plays anymore.