I'm so sorry for your loss. It is hard to lose these guys, especially when you do not know why.

Look on the ARAV website to see if there is a vet in your area that treats frogs. Keep your little one in the fridge (not freezer) until you can get him in. If you can't do it on Saturday, then go ahead and freeze him. If you can't find a vet in your area that treats frogs, you should be able to ask any vet to send the body to the lab for you. Most labs that are used by vets will do this. I don't know the cost off hand, but it is well worth it, especially if you still have one and are considering getting another. I would be concerned about parasites, especially if it is a wild caught (most are unless it is specifically stated to be a captive bred juvenile). You can pm me if you need help getting the frog sent in, or if the vet you end up taking him to has questions about how or where to send him. I have an excellent exotics pathologist I use that I can put them in touch with as well.