I have faced this multiple times. Actually it is the most prevalent and worst kind of cheating in this game.
You know something is wrong when your opponent loses one of his important units and then you suddenly lose connection and can't reconnect.
Um, ok. Well, you've completely ignored the technical points I made.
You skipped over the whole trust rating system, which almost completely negates the benefits of drop hacking if you do it more than once. Seriously, it's been around since COH1. So I'd hardly call it the 'worst' kind of cheating.
Also, if you're losing connection then there's pretty much no way that has anything to do with drop hacking. Drop hacking was when players talked directly to each other so they blocked your incoming data to confuse the game. That's now physically impossible. All players only see a server, not other players. Even DDOS stuff (which costs money) would require finding out your IP, which is probably impossible for the same reason. And all of that is way harder than finding a way to force a simple sync error. Seriously, they happen for so many reasons. One recent patch was to stop the game having sync errors when someone quit normally.
In a nutshell, it sounds like your Internet connection (or how your setup uses it) sucks and you've got a bad case of confirmation bias.