Not 20 years, but the incubation period for them can be several months, and most people will clear the virus within 2 years, putting you in that window of time for it to be from a previous relationship for either you or your partner.
So you could have gotten this from your partner early in the relationship, and not developed warts for a year, for example. You could have also gotten it from someone prior to your relationship and not developed symptoms until 6 months ago.
There is no test for men for HPV. For women, if the virus is not active on their cervix, it may not be detected.
If you are concerned your partner has cheated, this alone is not nearly close to proof. You will likely never know where it came from, and that's okay. If everything else is okay in your relationship, this is just a tiny little blip. HPV is now considered an inevitability of being sexually active. Some experts say that 90% of people will get at least one strain in their lifetimes, others put it even higher.