First of all UPS doesnt run anything except Saturday Air on Saturday. anything Next Day, 2nd Day, 3 Day Select or Ground will not show up at your house on a Saturday even if you order Next Day Air on a friday, you wont get it until Monday. So if youre mad at UPS over not bringing them on Saturday then youre mistaken because they dont run on Saturday.
If the Package is Signature Required, it's self explanatory you have to sign for it. No matter if youre in the bathroom or at work, if youre not there to sign when UPS gets there they cannot leave your package. He leaves a notice of what time he will be there tomorrow so you can arrange to sign for it. After 3 failed delivery attempts then its sent back after they try to get in touch with you to pick it up.
I dont see where any of this is UPS' fault. The shipper is the one who makes the package require a signature, not UPS. I dont see where UPS did anything wrong in this situation.