Have (or had) exactly 80k miles in my account.
Booked a Delta flight via phone agent on a partner airline in business for 80k miles. My account activity shows 80,000 miles redeemed for the flight, and flight is confirmed with confirmation number on partner airline.

But...I still have those 80,000 miles in my account.
I just attempted to book another flight at 25k miles, and it lets me get to the complete purchase page. If I choose a flight that is more than 80,000 miles, it tells me there are not enough miles in my account.