It could just be people independently working on the same things, as is common in technology.
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"Independent creation" is a valid defense for copyright, but not for patents.
Something cannot be patented if prior art exists before the filing of the patent. It doesn't matter if you knew about it. Even if you can prove that the prior art is not something you were aware of at the time you filed for a patent, your patent is invalid.
That's how patents are supposed to work; inventions must be "non-obvious" to the point where no one else has ever created it nor described it before on the entire planet.
If google knows that someone else has created such things (as they must have after said visit), the only responsible thing to do is not file a patent, regardless of if they independently worked on it.
A job interview is not a public disclosure and so doesn't count as prior art. So novelty is not affected.
However, the applicant must derive rights (employment, assignment) from the inventor in order to apply for a patent.
In UK IIRC S.13 of the Patents Act allows an inventor to file to be named as the inventor (or co-inventor) and for the patent to be reassigned accordingly.
Of course taking Google to court is going to be a hard slog.