Lost BRP while in Italy - how long does the vignette take?

I’ve lost (most likely, as I don’t think it has been stolen) my BRP while in Italy. How long does it take to get the vignette which allows you to reenter the UK once? I am travelling back on the 14th. Or is this something that comes through immediately? (I am not asking for the processing time for a new BRP, I know that’s separate).