Sink will not Drain

I have a post on the toilet forum that talks about my recent issues with a main floor toilet backing up. I have a plumber scheduled to come on Monday to look at that and i will be replacing the toilet.

My son just came to me and said that when he flushed his upstairs toilet he heard gurgling out of his sink. The sinks in that bathroom are a double vanity and I am now finding that neither of those sinks will drain water. The toilet up there flushes fine.

It is very cold here and I am wondering if I have a frozen drain pipe. The plunger didn't help. I also ran some hot water in the sink and that is just sitting there.

Any ideas on what I can try? Should i put in some draino?

Sounds like a blockage in the main, you will need to have it augered and I always recommend scoping the line with a camera after to find out what caused the problem. Draino won't work and can be dangerous for the plumber so don't use it or if you do let him know that you used it!

IF the main was blocked, wouldn't I have a problem with the toilet that is in the same room, the bathtub/shower in that room, and other sinks?

I would clean the pop-ups on the lav first. They tend to collect hair.
No draino, it's pretty hard on pipes.

What are the pop ups? What is the Lav... the Sink? The drain stoppers are out of both sinks and I did try the plunger. No luck