What you are speaking to relates to sample size for everything to bear out. We would not speak in terms of ten if dealing with pea plants or fruit flies, so likewise I would not pre-conclude with snakes. But unless one plans to create 100 neonates, there is a personal call to make.
If you want to compare coin flips, then do so on equal footing. Not 1,000,000 times, but the number of times the OP has had eggs with results he can determine. My father won a betting contest in his home country in his town square where he flipped a coin a dozen times and got the same result. He used that money along with other savings to help him come to this country. A fluke and nothing more at that sample size. Wonderful for him because it worked in his favor, but luck could have just as easily not favored him.
If I had a clutch of ten from homozygote x "heterozygote" with no homozygote neonates, I would become suspicious. Two clutches? Near sure (confident) for me and I would at this point reconfigure my project to accommodate an inability to rely on her het status (basically get a backup plan). Three? Sure enough for me to consider her disproven for the sake of my project, although it is still remotely possible (one could argue you can never technically disprove the animal via test breeding and that the probability just approaches some infinitely small chance, but -as I have maintained- there comes a point where a call must be made or one can remain in a useless limbo).
I agree that a lack of response is concerning. I should also point out that I am not trying to defend or accuse anyone here. I am simply saying this should be carefully evaluated in its given context. If I breed a visual male to a supposedly het female and I get ten hets, that does not mean I do or do not have a het dam, nor does it mean I am "owed" or should expect a neat case of five homozygotes and five heterozygotes, although lacking one visual would start my suspicion train rolling at least a little. I would still consider it my responsibility to give the female additional attempts before making a strong and damning declaration as to her status and the nature of the business deal that brought her into my possession. When I bred leopard geckos, I had seasons where a het eclipse female bred to an eclipse male produced all eclipses, I had a second season where she produced none, and then a third season with a relatively even mix. Same female. Always bred to an eclipse. If the second season's results and the first season's results were switched and I cried foul, I would have been incorrectly describing the genetic nature of my animal and I would have unfairly made a false claim against the seller when inadequate justification existed.
