Diagnostic info in settings

[J hind]

My husband secretly talked on e buddy with another woman years ago I found out again by the diagnostic log on his I phone he had been on again on five consecutive days while we where arguing after confronting him he denies any knowledge I went to show him what I had seen and it had disappeared in hours please can someone tell me a. Is it possible to be in the diagnostics without inputting the site on private browsing and b is it possible to personally delete from the log he is adamant he has not done it and says its me being paranoid I know what I saw and still he denies this ! divorce is looming now after 30 yrs of marriage sadly on my part as he will not admit to it please please can someone advise so I know it is not me going looney thank you