Back in the old days -before everyone was building Pro Stock and F1 engines and we didn't have the benefit of the Internet- we, well a lot of us, anyway, would have just plopped the lifters in the bore and called it good. As long as things were clean and fit well, all was good. And you know what? The engines ran good and performed as they should. Yeah, we really did that and it was common.
It should go without saying you will bring the ire of the collective forum should you even suggest such a thing could be done. I understand the argument that a pack of new lifters and a repeat break-in is a small price to pay. Hard to argue against that, but I suppose that is really the nature of my opening statement. I do fully understand what is going on with the cam and lifter during the break-in. Don't bother explaining that to me as if I were an imbecile. Would you be okay just dropping them in a bore? Maybe and probably yes, but no guarantee of success. But then, you run some risk with any flat tappet cam with all new parts. So, for that reason, you need to run a roller cam.
Edit: I wanted to add that I would probably replace them since they fell, you don't know if there is damage not apparent to the eye.