Teams is gone from left-menu in Teams

Did your "Teams" square/pin/tile disappear in Microsoft Teams?

Why'd this happen?

This is not uncommon, there was likely a feature update notification in Teams that you just clicked through to move-on with your day. It happens, no worries.

Resolution:

In the upper-right within Teams:
1. Click the ellipsis to the left of your initials/image
Click Settings
Click Chats and channels in the Settings menu
Look for the Combined and Separate tiles
Click Separate