What abilities do Admins of Gsuit have?

Recently I was jolted away from the naive world I used to live in. I received an email from a manager in the company I work for. Quickly noticed that I wasn't supposed to be reading the poor performance evaluation of one of my co-workers and that everyone else in the company was also copied in the email. Probably a common enough snafu that should be followed by a sincere apology and pleas not to read. Instead, after five minutes, the email disappeared from my inbox and all other inboxes in the company. No follow up email explaining or apologizing. Just a pure cover up. I am left pondering if anything in my work mail box is reliable. Have they deleted stuff before? What can I do to keep proper records of my email communications? What else can admins do in addition to visit everyone's email inbox and deleting a particular email?