A mania (obsession) with recalling a certain forgotten word, or words.
Better write this one down -- it drove me crazy for weeks. I kept searching the 'logo-' sections of every dictionary I could find. Who knew! Logo- is shortened to log- when it is appended to words starting with a vowel. In this case it is being appended to anamnesis, which refers to remembering the past.
Pronounced LAG-an-um-NOH-sis or LOG-an-um-NOH-sis.
See also logomania* and lethologica.
* Yes, I know that logomania doesn't technically mean a fascination with words, but people use it that way. A logomaniac should be possessed of logomania. You logophiles might prefer to be refer to your obsessions as logophilia, but let us not logomachize. I am a logastellus, not a logogogue.