Toilet flange to shower pan seal

[GOWINIGO]

So I have searched high and low both on this site and around the world.  I have removed the toilet flange in my 76 d21 to fix a leak and now need to re seal it to the shower pan. Is this just sealed with silicone as I thread it back into the black water tank? There was no evidence of a seal or even silicone when i removed it.  The reason for removal was when the shower was used it would leak around the toilet flange to the outside.

[Oz]

Should have a seal.  Of the 3 I replaced, I just bought the standard one at Wal-Mart and it worked.

[GOWINIGO]

Thanks for the reply, 
I ended up applying silicone between the flange and the floor. There was no groove for any type of gasket or anything. This isn't the toilet to flange seal but flange to wet bath floor seal  :/ Also there wasn't anything there when I removed it. I'm thinking either the P.O. didn't install it when they replaced the toilet or it is just "glued and screwed. After the tub/tile paint dries another day I can test it. I will make sure to report back.