A truly bad story but there are some things we can learn from this debacle.
1. These things seem to happen at large banks. Really no surprise there, they are always consolidating, selling, transferring and staff turnover can be high; standards are often lax or criminal as we have seen at Wells Fargo. Yet I'm sure there are some OF members who still bank there. It is worthwhile to seek out a smaller, community bank for your banking and SD box needs. You know them, they know you.
2. Don't ignore correspondence from your bank, the victim always claims 'I never got the letter', but it was probably overlooked, ignored, thrown out, spouse opened it and never told the other, whatever. Keep on top of your financial stuff.
3. Don't put stuff in the box and leave it there for years. Go in to the bank once or twice a year, sign in, open the box, make sure everything is ok. Make sure there have been no unauthorized intrusions.
4. Do not automatically assume that if you insure your watches that you are on easy street. Unless you have strict documentation, recent appraisals, receipts, photos, etc every insurance company is going to scrutinize a claim, especially if it is a massive loss like what occurred here. An insurance company will look for every way possible to deny, or reduce, any claim of loss. Don't get complacent on values.
Personally, I live in a town of about 12,000, I've been banking at the same bank, which is part of a small bank chain, for over 16 years. Although the bank has changed hands several times the people remain the same. I have no fear that they are accidentally going to drill my box open by mistake. But if I was in a large city they probably wouldn't know me from Adam, and wouldn't care. So choose your bank carefully, in this case small is probably better.
And let's remember, losses like this are very rare, most SD boxes are never tampered with or broken in to, or what happened in this case. Keep it in perspective.