Were your fingerprints taken as part of this application?

I came to the UK with a visitor visa (17 years ago in 2003) and with a student visa (8 years ago 2012). I cannot remember if for these visa applications my fingerprints were taken or not. Unfortunately I cannot select in the citizenship application form an 'I don’t know' option (it's either yes or no). What do you suggest I do in this case?
I've read on news articles online that fingerprints were not taken for all countries prior to 2017... but I cannot find a list of such countries. So I cannot tell if for Colombia (where I come from) this was required back then.
If I select 'yes' and then explain in a cover letter that I'm not 100% sure if my fingerprints were taken or not back then, would the citizenship application be rejected? Thanks.

Student visa would definitely had your biometrics (photo and fingerprints) done 8 years ago.

I've read on news articles online that fingerprints were not taken for all countries prior to 2017

Finger prints have been mandatory for all applicants since at least 2008.