LITTLE LEAGUE CLARIFICATION - ASAP

[IndianaUmpRef]

Our district starts their 12's championships tonight and I need a clarification. I usually would know something like this, and thought I did, but I need to ask. I do 55-65 high school games a year and then switch to little league in early-mid June every year. So I never really brush up on LL rules as much as I should. Anyway, here it is:

R1 on second base. F1 pitches a passed ball. F2 sees the ball trickle behind his feet. R1 runs to third base. F2 picks up the ball and throws to F5 at third. R1 slides into third and kicks the "breakaway" bag out from the ground and about 5 feet into foul territory. The throw from F2 went into the outfield, where F7 was backing up the play. R1 runs home, F7 throws home to cut down the runner. The runner changes his mind and gets into a pickle between third and home. After a couple throws in the hotbox, R1 decides to slide back into third base, but their is no BASE. Whats the call?

I always ASSUMED this was an automatic dead ball situation because who knows when that base might become in use by a trail runner OR what if the runner must retreat BACK to that base? But, every umpire I talk to gives me a different answer, mostly because a lot of the umpires in our district our high school umps by default. Can someone help me ASAP. I might have some follow-up questions to this if the answer warrants it. Thanks.