Dear postal worker - these are worth millions and millions of dollars. Please don't toss 'em!
On suggestion of Laurel in my comments, I looked into a postal Lost and Found. I didn't find anything online so I called their 1-800 number. A tip, if you keep saying 'customer service' over and over even when it isn't a choice, they will kick you from the machine and finally hand you over to a person.
Anyway, all items found outside of their packing are sent to Atlanta. Then somebody looks them over and decides if they are worth more than $10. If not, they destroy the item. If so, then they put it on some shelf and try to find the owner. The lady took all my info and I have an official case number. They are supposed to call in 2 business days either way.
I may not get my blocks back, but that was a very interesting process. And these little blocks didn't die in vain, as it seems many of you will be using lots more tape now!