Realistically, you won’t be asking her to re-alert on a truffle in a hole after you have given her the ball in the field. She won’t get the ball until you pick it up. The criteria for getting the ball will be a truffle in your hand. So, it likely won’t be a problem. She is motivated enough that you can start picking up the truffle and having a party with the ball. She will likely start offering 1-2-3 nose targets to get the ball. That’s a good thing. It builds persistence. “Dad, it’s right here! Pick it up already!”
You might be surprised what happens when you allow her to keep the ball! One of my dogs highly values possession. Sometimes we train with a toy and I never touch it! They often value the interaction with you more than the object itself. Just make sure that Molly sees it this way…
Object alone (possession) – mildly/ moderately rewarding
Object + you – MASSIVELY rewarding regardless of who “possesses” it.
Sometimes, they stick around more when they realize you aren’t going to take it from them. What is the act of taking it from them anyway? It’s interaction with you and the toy. It’s a game that we don’t enjoy.
If you allow her to keep the ball and send her to hunt again, she may just drop the ball once she catches the scent. It’s hard to sniff with a ball in your mouth. Not that it can’t be done and she just might. She will soon realize that you have an unlimited supply of balls and the one you have is ALWAYS more exciting!