Lender gave me a 3.875% apr closing disclosure possibly on accident, can I keep it?

I am in the process of a VA IRRRL and I talked to the loan officer and we basically agreed on a refinance from 5.875% to 5.375% over the phone. So tonight I get a notification from Rocket Mortgage saying to sign the new closing disclosure and it shows a rate lock that is only good 7 days (weird) but it is in fact, signed and locked by the lender at 3.875%. The package also includes the closing disclosure documents with the entire loan breakdown and seems like the 3.875% has to be way too good to be true, but it is all legit. Would I be able to keep the rate that they offered? Or is there any way that they can weasel out of it even though they signed it and claim ignorance or incompetence. I just signed and agreed to the disclosure package in the Rocket Mortgage portal and it in fact says I signed it and is now a task 'completed'. Is there any way I can ensure that I keep this rate and what do you guys recommend I do? Its so weird I cant find anyone who has ran into this before. Thanks.