The MXS-r is an acrobatic aircraft. MX Aircraft MXS - Wikipedia
I had a similar issue with one of my installed Marketplace aircraft disappearing. If you do a clean install of MSFS remember to delete the contents of Users<you>\AppData\Roaming\Microsoft Flight Simulator before installing. Then install your Marketplace purchases one at a time with a restart in between each one. Use the same strategy for your Community installs.