I was hacked on the 8th/9th -

Since the password was already reset and sign-in activity was reviewed, the next checks are in Outlook.com itself:

1. Check Archive, Junk Email, and Deleted Items.
   • If a message was archived, it will not appear in Inbox.
   • In Archive, select the message and choose Move to > Inbox.
2. Check the account’s Recent activity page.
   • Review sign-ins from the last 30 days.
   • If activity is not recognized, use This wasn't me or Secure your account where shown.
3. Check Outlook.com account settings that are commonly changed after a compromise.
   • Review connected accounts
   • Review forwarding
   • Review automatic replies These are specifically called out because compromised accounts may have had settings reset or changed.
4. Run a full malware scan on the PC before changing the password again.
   • Open Windows Security.
   • Go to Virus and threat protection.
   • Select Scan options > Full scan > Scan now.
5. If mail is still not arriving, use the Microsoft Sign-in Helper.
   • It can provide self-help steps or offer the chance to talk to an agent.

For older missing mail: check whether the messages were moved to Archive first. If they are no longer in mailbox folders, the available context only supports checking those folders and the account activity/settings above.

References:

• How to recover a hacked or compromised Microsoft account
• Email is missing from your Outlook.com inbox
• Help protect your Outlook.com email account
• What happens if there's an unusual sign-in to your account
• Unblock my Outlook.com account