Ouch! I hope it gets resolved quickly.
As you noted, it’s a big and heavy box, so it seems unlikely that they would sign for you and dump it rather than ringing the doorbell. At 79lbs, our UPS driver wouldn’t even take the big box out of the truck without first making sure that we answered the door. (Then again, we put a big sign on the front door that said, “UPS! We are home! Ring doorbell!”)
Then again, UPS has had their share of delivery issues. I’m still stunned by the one where they delivered a mattress by mistake: GlowForge or a mattress?
(With all of the damaged deliveries that people have mentioned in this forum, I really hope that GF is over-insuring the packages and turning a profit on UPS’s mistakes.)