The only other time was when my kids were babies; I guess they didn't want the babysitter in their play area...
But seriously, all these things, as De Sitter spaces, gluon strings, etc., are hypothetical. I truly wish there was either an alternative to the string theories and the standard model, or at least a more "beefed up" standard model that not only has its general all-around accuracy and facets that might point the way out of the "missing mass" or "wrong direction shifts" problems we see in astrophysics...
... anyway, as far as I recall, no one has truly "observed" quarks, either, though the predictive mathematics behind it is established...