In December I took a nice coyote. It was skinned with an hour or two (was cold and snowy), and salted. It was put in the freezer for a few days.... and forgotten.

So, can I still tan this hide (hair on) or is it too late?

cas,

If you wrap it up good, It will last a long time. I'm talking years.
I wouldn't worry about that.

oct71

Cas:

First of all, if the skin was salted, it won't freeze. Salt prevents freezing. How long has the skin been in the freezer? It may still be good after a couple of months at most, but after that, you run the risk of having the hair slipping when the tanning process is started. It is better to either salt the skin and allow it to completely dry out or to just freeze it without doing anything else to it. Hope your skin is still good, where I'm from, good dog skins are hard to come by.

Regards, Wyo

Wyo is right. The salt will not let it freeze and if you ever salt a hide, let it drain and then salt it again and hang it to dry.
If you have a freezer, wrap it in a plastic bag and remove as much air as you can and then slide it into another bag. Once frozen it will last for years.
As far as your pelt, take it out and wash it with cold water and Dawn soap and then rinse. If the hair hangs in you might have gotten lucky. Bag it and freeze it if its still good.