My spouse had an affair

My spouse is an officer and was having an affair with another service member. I caught them and had evidence. I was angry and embarrassed and hurt. So I went to a friend's and vented. Told them everything, showed proof. They then had their spouse file a complaint on my behalf to the IG. I dont want an investigation. I no longer have the evidence. I was the only one with access to the evidence. When the IG calls me back today can I lie to them and say this was a misunderstanding? Or just ignore them? If they dont have evidence and no one confesses will they just drop the investigation??