I open my project in Xcode 6.1. When I try to run the project, the button is grayed out. When I try to go to Product > Clean, the option is grayed out. When
Product > Clean
Small but a effective solution. In my case i updated to my xcode to 9.2 version and simulators disappeared.
I found this solution and it worked for me and for others also.
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Just quit your xcode and restart again. You will have simulators.