Postal Service, you are letting me down

I'm not one hour back from my trip and I'm already stressed and upset. I come back to an inbox chock full of emails, and find that a few of them are about fabric orders that have gone missing in the post. Now don't get me wrong, 99% of the time packages arrive safe and sound (so don't start worrying), but to receive 3 emails at the same time about missing parcels was just too much for me to hear.

What I'd really like to know is, what is the correct etiquette when it comes to missing orders? What do shops usually do? I always resend the fabric if I have it (or another as a substitute) with no questions asked, but I'd love to hear what other people do. I hate the idea of an unhappy customer, so I'll do anything to make sure they're happy ... even if it means having to take responsibility for a crappy postal service or some nasty person who steals parcels out of mail boxes. Some shops put a "no responsibility taken..." disclaimer on my site but that just seems so cold and unfriendly and in the end doesn't make for a happy customer! Thoughts?

[update] Well, I feel better about the whole thing now - after talking to a few people and also reading the comments. All basically reinforcing what I already know is the right thing to do, which is to just take these losses as they come and replace any missing orders. Mum suggested to 'self insure' - which is basically to factor into your costs the possibility of one or two parcels going missing, so that it doesn't hurt too much. And I like that idea. Registered/Insured post in insanely expensive around here and just isn't an option.