Ah. I see your problem. You think the evidence of a differing air mix before the flood means anyone else's speculation (outside your own) that can be dreamed of, related or not to... anything... is being claimed as valid.
This is patently wrong. A differing air mixture, plus the other evidence I've listed, has a set of reasonable possible causes. One is a canopy. Pink elephants are not.
To take your syllogism the way it is without stating my position correctly, it is saying that because something is a possibility it is necessary. In this, you are simply being illogical. I'll state your syllogism again to make clear the vague statements:
- I believe that the atmosphere was different before the flood (based on scant evidence).
- A different atmosphere could have allowed for the possible existence pink elephants
- Therefore, pink elephants definitely existed.
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As a tangent (and this is the benefit of continuing with this discussion), trying to create a syllogism to find the logic of a hunch usually ends up to be worthless unless the context is the logic of hunches themselves.