I've long realised that BA re just a big slab monolith of a corporation & people's blind loyalty to this company is completely misguided. In all reality & when the chips are down they (BA) couldn't care one jot about an EC member. For me it was quite the liberating moment when this dawned on me.

To those who berate the OP for not paying attention or not doing his sums correctly then go on to say, "somehow it's BA's fault" Well many companies, clubs & organisations are able to advise their members in advance of their membership expiring, or an impending failure to re-qualify.

For example the AA can send out a mail shot saying that your membership is coming due for renewal. Sky can send out a circular, offering you the chance to upgrade your subscription. So why can't BA, as the OP says, send out a communication to the effect that his Silver tier is due to expire & why don't you take a trip to bolster your TP count so as to retain status !!??

It would not only show a customer focused policy by BA, but it might also prompt the sale of a couple of extra flights to boot. I'm sure it's not difficult to have such a mail shot automated & I'm equally sure it would go a long way to impress the customer, while at the same time retaining business.

So to the OP, you have my full sympathy & I would go on to say that it borders on negligence on behalf of BA not to be pro-active in keeping their BAEC members informed as to their potential loss of status.

A small thing that would help protect future revenue.