Hi @JustinMicheal-7973
Have you tried searching the mails in OWA and get the same result? Could you please check if you applied any retention policy/tag on the folder or items which may lead the mails get deleted? Do other users have access to this mailbox and may mistakenly delete the mails? Can you see the mails in recovery folder and restore them?
In addtion, you could also try using eDiscovery to search the email items in the online archive: Search for content using the Content search tool
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