Could be bad news, but you might be lucky. Unlikely I suppose, but did you have aircon on? I had a problem with a drain pipe from the aircon condenser which caused water in the passenger footwell.Can't help on TSB you're after, but have you had a look, yet, for possible ingress points?
If not, then do search on here as there's masses of information - some solutions, eg. loose wheelarch bung, are 10-minute jobs so not arduous to do