Lien help (Denver)

I did a $40K+ job for a big client, collected 50% upfront, and finished the work in November. They still owe me the remaining 50%, but I just got a letter saying the apartment complex is being sold to a new owner.

I’ve been in contact with the regional manager, who assured me I’d be paid, but the sale closes on February 7. I’m worried I’ll get stiffed.

Is it too late to file a lien? Should I file one today? I really don’t want to be out $20K, but it’s looking like I might be. Any advice?

Edit: My client reached out and sent me a Check number and a tracking number. Freaking out for nothing!