I bought 2 teleport spells in order to complete the hidden rooms in Urhig's Gaol and then get back to the portal. However, one turn after the using the first one, the second spell had disappeared from my spell book leaving me stranded. Is this a glitch or a peculiarly of the teleport spell?
Sorry about that, I'm not sure what could have happened there. There is no reason for it to disappear. I just did a quick test here and could not immediately recreate it, so it must be something unusual. FYI, you don't need teleport to get there, there is a hidden floor panel that opens it up. Unfortunately there is no way out if you teleported in, sorry.