There's no such thing as a chain of disappearing transactions in BTC. And it you heard something about it, most likely it's a scam.

Although there is a good discussion about a Fake walle.dat can trick bitcoin core client?.

So to answer the question is it a threat? No.

The best advise is that continue to accumulate we are getting to the block halving, and next year could be the start of a massive bull run. Better be ready.