Hi OP, I work in sexual health.
If it reassures you at all, I’ve treated patients who haven’t had sex with anyone for years and suddenly develop a wart. Usually they’ve been unwell with something else or stressed, run down etc.
The way I usually explain it to patients is that our immune systems are only really good at dealing with one thing at a time, so when something more serious comes along, it ‘forgets’ to suppress the wart-causing HPV (if the person is a carrier, of course) and a wart might appear on the skin. Doesn’t always mean anyone has cheated as it can often take quite a bit of time for one to show up, if it ever does! Most people are asymptomatic carriers of some strain of HPV at some point in their lives.
To clear up a misconception posted by someone upthread, genital warts categorically do not cause cervical cancer. The HPV strains that cause warts are different to those that can cause cancers. Genital warts, whilst they can be a bit unsightly or uncomfortable, are otherwise harmless.
You also wouldn’t qualify for an HPV vaccine via most GUM clinics as most guidelines suggest it isn’t worthwhile past a certain age as you’ve statistically more likely to have been exposed than not (I can’t directly quote current guidelines as I’ve been on maternity leave for months and they may well have changed in that time!)
Home treatments are available for your DP, can be prescribed in GUM but can take longer to work and you need to either not have sex, or be on reliable contraception (or if DP has had the snip) as the home treatments will cause condoms to perish and are harmful to a developing foetus if you were to fall pregnant.
Sorry for the bloody essay! You can PM if you need to 🙂