The word I found that seems to be very close to what you need is
\"whoosywhatzit\" (slang)...used when you don\'t understand what the person is saying ( someone might be talking with a lisp, mumbling or just blurting things out).
Almost like \"thingymabob\" or \"thingymajigger\" when you talk about a thing.
Maybe \"Whoos\" might possibly be a substitute for someone you can\'t rememeber ?????...
:)