I woke up this morning to find that my spa is completely dry. My spa is elevated and overflows into my pool. My filter was running with no water running through it (hopefully I caught that in time). My filter usually runs daily from about 8:00-4:00. Any idea what caused this? It might have gotten a hair below freezing but that shouldn't have messed with anything.

Here's my guess: your freeze protection kicked the pumps on when the temperature dropped below a certain number, but the valves were not in the correct orientation so the pump drained the hot tub in to the pool?

I'll double check that when I get back. That makes sense and I should've thought about that. Thank you

The bottom of your spa is completely above the pool level? If so, could be a leak in the check valve.

yep, check your check valve going to your spa pump.