How long do you hide these chats?
Are these meetings organized in your organization? If so, please note that recordings aren’t stored in Microsoft Stream but are instead stored in Azure Media Services (AMS) with a 21-day limit before it's deleted when organizer has no Stream license.
I tested in my client. It can search for the hidden meeting which I hide last year.
You could try to use the Content Search tool in the Security & Compliance Center to quickly find the instant messaging conversations in Microsoft Teams. For more details about how to use Content Search tool, please refer to this article: https://learn.microsoft.com/en-us/microsoft-365/compliance/search-for-content?view=o365-worldwide.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.