Neither side is going to recover it, but again, if the giant AllSpark is seen deep within the confines of Sector 7’s Hoover Dam and no further mention is made, that’s why.
Prime’s plan will ultimately prove successful, and while the AllSpark ultimately is destroyed, it’s still a highly sought after object during the time of Bumblebee.
No doubt the Decepticons will be searching for the AllSpark in this story, provided they have the same information Megatron had when he went searching for it long ago.