By investigation, what do you mean?
There isn't going to be an FBI investigation, for two reasons:
Statute of Limitations
Allegations, even if true, would not be a federal crime.
Therefore, any investigation would be done in congress, using testimony from the accuser, and or witnesses. If the accuser can't recall the exact date, place, time, purpose of the party, etc., where does that leave us? If she refuses to testify, where does that leave us?
It leaves us where she has not demonstrated by sworn testimony that this happened and absence of facts, or having foggy memory, will destroy her credibility when she is deposed under oath. All she remembers is that something happened and she dropped a name. Who administered the polygraph and what was the line of questioning? I don't know...do you? Do you believe a polygraph to be a lie detector, where the results are an absolute true or false?