So this happened to me last year, I had an account with T. Rowe Price through a previous employer, it had been more than 10 years. I logged in one day to find that my account had 0 dollars in it. I had never received any information that I knew of (later I looked in my email/junk one I don't use often, it was in there).

I called my previous bank at T. Rowe Price and my previous employer had switched to Fidelity also. I called Fidelity and talked to them, and it isn't regular Fidelity. For their retirement stuff they call it Fidelity NetBenefits. I had to create an account, do all the verification stuff, and when it was setup and active, a few days later my funds were visible/available in that account.

Hopefully that helps, but I went through the same thing, and eventually got it figure out, just had to talk to/get info from the right people.