Astronuc said:
To my knowledge, no nucleons based on combinations (ccs or ttb quarks) have been produced in this part of the universe.
True, although there are "hypernuclei", where one of the nucleons has been replaced by a hyperon, most often a \Lambda^0, but a\Sigma hypernuclei have also been produced and studied. There are people who dedicate their entire careers to the study of hypernuclei.
This field has some surprises: {\rm ^5_{\Lambda}He} should look a lot like {\rm ^4He}, but in fact, unlike the alpha particle, is not very tightly bound at all.
The problem with (css) is that it's pretty much at our limit of abilities to produce a hypernucleus with one strange quark, let alone two, let alone charm. But this is a practical problem, not a fundamental one.
Astronuc said:
Muons don't exist long enough to produce an atom that could be investigated.
That's not the case. A negative muon can be captured by a nucleus, and it can live long enough to undergo atomic transitions, giving off x-rays as it de-excites. These mu-mesic x-rays (as they were called when they were discovered by Val Fitch and Jim Rainwater in the early 1950's) provide a lot of information on the charge distribution of the nucleus - because a muon is 200x heavier than an electron, it's Bohr radius is 200 times smaller, so the effect of the nuclear charge distribution (e.g. quadrupole deformations) is orders of magnitude larger.
Indeed, the lifetime of the muon is about 20 trillion times longer than the classical orbit period. Microseconds seems like a short time to us, but compared to typical atomic transition times, it's huge.