It is a good idea to expect the worst. Have a portal in or near one's HQ named "Emergency" or "Backup". I got lucky recently, I got stranded similar to the OP. I had unintentionally reset my spawn point to a remote island shelter I had just built. While taming a couple of Lox, I was attacked by 2 Deathsquitos, which would normally not be a problem for me, but the completely hit me by surprise, scaring the hecoutta me, while I was low on health after fighting Fulings, while wearing Troll-Hide gear, rather than my Padded armour. I had enough materials on hand to build a portal, and lo & behold after building it, it said, "Connected" before I could assign it a name. I had an unnamed portal back at my HQ. I was surprised that that worked as a connection, having 2 unnamed portals, but it did, and they all lived happily ever after.