This has happened to me too with a couple of friends some years ago. Drifted off after some years of being friends - and couldn't be arsed to contact me/respond to emails and (written) letters from me, so I thought 'well fuck off then.' 
Then about a year after my last contact to them (and about a year and a half after theirs to me,) I got 'oh hi how are you BatchCookBabe???' Haven't spoken for a while have we? Must get together soon.' This would be via letter (or email or text.) I got back in touch, all was OK for 1-2 years, then they stopped contact with me again. 3 or 4 letters, and several emails later (over 8-9 months) and nothing from them. NOTHING.
Then about a year after my last contact I would get a text or email saying, 'oh hello again BatchCookBabe! We MUST catch up!' Then the same thing happened, I responded, we were mates again for a year or two and then they ghosted me again... So eventually, (by the 3rd time,) I just ignored them, and ignored them. Even blocked their number... Then they contacted me on Facebook, so I blocked them on there.
Both of them (1.5 to 2 years after I blocked them,) tried to contact me via an old mutual acquaintance/old friend, to see what had happened and why I hadn't got back in touch...' Said person said 'here's their phone number, get in touch, they want to meet up!' OR 'you need to contact them, they've been trying to make contact with you.' I said 'oh yes of course...' Then just threw the phone number away. I don't get treated like shit over and over. Fuck that shit. They actually seemed annoyed that I ignored them, over and over. Yet that's what they did to me. At least twice!
The only time these 2 friends (separate ones who didn't know each other) got in touch was when they wanted to brag about something. New car, new man, new house, new job. When their life started to get a bit basic, and not how they wanted it, when they had just been dumped/became single, when they were broke and in a shit job, they didn't stay in touch with me. I believe they were a bit resentful of me being happily married, with a nice home, lovely children, a decent job, and a nice car. As soon as they got at least 3 of those things, they wanted to be friends again. Nah mate. Fuck off.