Need an additional ticket closing category

[#1]

I have had several days of low download speed on the FTTC connection. I ran the appropriate test and after several days the speed returned to normal. The response on the ticket was no fault found and performance is normal.
In closing the ticket I have only one option - that means that the Fault has been cleared and resolved. I want an option that indicates that the fault was not identified or cleared but it evaporated and the problem could still be around to strike again. Perhaps a Question Mark ? or whatever the symbol is for a shrug of the shoulders.
 

[#2]

In those circumstances do what I do
Don't close it and about once a week add a comment to stop it self closing until the problem really appears to be solved

[#3]

Hmm, as drw points out as that is the only option, using it makes it look good on Plusnet's statistics when in fact they haven't done anything. I think your suggestion Jim is the best in the absence of another sensible option, at least the "fix" time will perhaps make up for the initial misleading "fixed". In drw's case, I'd have certainly addded to the ticket saying that the fact it was NFF was because it's either intermittent or has just "disappeared"