Am I a possible victim of identity theft (United Kingdom)??? I'm PARANOID

It all started when I applied for a tax refund (I did my SA at a LONDON IB firm), but because I live far away in a non-European nation, I had to nominate a friend in UK to be the recipient of the Tax Refund Cheque (as my "Nominee")—however—HMRC had made a mistake on the cheque, because of which my Nominee couldn't cash the cheque. HMRC promised to re-issue a corrected cheque, but that I would WAIT an extra 6–8 WEEKS for it to be sent.

There was this PhD student in Oxford University—a native of my home country—with whom I discussed the situation with on WHATSAPP. She promised to reach out to some lawyer in her university who does pro bono work for ethnic minority immigrants, and who could perhaps get HMRC to re-issue a corrected cheque with a significantly SHORTENED wait period (instead of the extreme 6–8 weeks I had been told), and perhaps even receive extra monetary compensation for the inconveniences through litigation-ish attempts (HMRC had made several multiple errors corrected over multiple calls ever since I applied for the refund in March).

Long story short—I had sent my P85 PDF & the picture of the cheque in which HMRC made an error to this PhD candidate who promised to put me in touch with a lawyer—and I noticed less that 24 hours later that I HAD BEEN BLOCKED on WHATSAPP.

I don't know whether or not to be paranoid about the fact that she (the Oxford PhD student) has my P85 (& picture of the HMRC cheque containing the error) which contain my sensitive personal information like date of birth, National Insurance Number, past & present addresses (especially my former UK addresses), etc.