So I Do I Have Health Insurance I Need To Pay Or Not?

OK, so while I was at work I get a personal e-mail on my work e-mail address.  It tells me that I have an outstanding claim, one that my insurance claim said they have provisionally paid, but I need to upload documents or else I'll have to pay it back.

Damn, this came out of nowhere.  Moreover, I am surprised I'm getting this on my work e-mail -- so much so that I flagged as spam, but the IT department at work said this was legit.  So I took a few minutes to go back onto the insurance website (to the point where I had to change my password because I forgot it -- you know how that goes, right?) and, wouldn't you know it, there was a claim that the company is questioning.  I don't even know what kind of documentation they would need.  I feel stuck, and I'm scared that if I don't respond to them soon, I might be told to pay them back.  And it's a chunk of change I can't necessarily just part with without wondering how I "lost" the money.

So I decided I would look at this again at home.  I might have the documentation on my personal computer, and if not, I would have the time to research exactly what is going on here.  So I get back onto the website ... but the claim I was looking for isn't there.  Moreover, the website looked different than the one I went onto at work.  I wasn't ... phished, was I?  My IT department said this is legit, so is there some other explanation?  I need to reach out to the insurance company, but this is kind of weird, man.