Incidents like this are why I know aliens aren't in Area 51, and generally believe that the government isn't withholding some huge bombshell secrets from us. Not because they don't want to, but because they can't.
In the event of any kind of info leak, discretion is thrown to the wind and FOMO sets in. The urge to "correct the record" becomes overwhelming. Information becomes a currency to spend. Only the best 3 letter agencies in the world can resist, and even they are only as strong as the weakest-willed.
Time + workforce churn = inevitable leaks for just about everything. You might be able to buy yourself a year or two with loyal employees and strict secrecy policies. But retaining a HUGE secret for 10+ years? Not compatible with society imo.