Had a bath, thought about it some more 
So, she had several that vanished. One had been so in to her beforehand (for circa 3 weeks) that she couldn't believe he'd just vamoosh so she kept texting but got nothing back, not even to a 'Look, I get it, you're not interested but just let me know you're alive pls' text. I texted him from my phone and he answered straight away, so not dead, no lost phone etc 
I think maybe some of them were deeply sexist. She was quite 'out there', happy to DTD wherever whenever, the blokes were always remarking on how she was the 'best girlfriend ever because she 'let them' [insert random sex act here]' which she took as a compliment (!) And I think that they thought 'werhay' this is great but [massive cliche] I wouldn't take her home to my mum'. So they weren't worthy of her anyway.
Never had it happen to me, had lots of dating disasters but no vanishers. One night we met two men, got chatting, all was ok. On way home she asked me what the man I'd been chatting to had been like, I said fine, talking about English, politics etc. She was all 
the man talking to her had been asking if he could do her up the ass! (I've cut the story short but you get the drift).
The only real difference between us is that I'm quite cold and very shy so I give off a 'don't touch' vibe I think. Whether this deters the wankers I don't know?
She was often dumped 'cruelly' by having people vanish etc, and I think maybe they were embarrassed that they'd been so 'I lurve you' that rather than have a proper conversation around 'As time has gone on I think we're not right for each other' they just had to slink off because of all the crap they'd spouted before? And perhaps blame the other person for being too 'forward/clingy/wanting a relationship' so they could excuse their behaviour to themselves?
If any of that ^^ sounds like I'm blaming the person who had the vanishing happen to them then I'm not, just musing while other half (who I met on OD) watches the rugby.