KrazyKat: not to sound arrogant, but my English is fine, thank you. As you properly pointed out, "Jona, or something like that..." suggests that you tried to guess the entire name, as opposed to "Jona... something" where it is implied that you only got a part of it right, but don't remember the rest.
I know that, in English, they might not be technically the same thing. However, if the concept of expressing uncertainty of a word (complete or partial) in Japanese can be translated into "...something" or "...something like that" I'm ok with knowing either, although my original intent was something among the lines of partial words.
You are right, though. While technically not the same, that might be something specific to English and not to Japanese (just taking a shot in the dark, here).