If you can't see 'em they aint there ...some trees put them out yearly some never do some do some years and not others , some have so few that if they are a large tree you might miss them.
And if you had this past springs freeze you will probably not have ANY seeds this year I have just a few on a couple of my older trees unlike last year where many had them ...
Dissectums seem to have less and often none and older trees often more...
And rememember as always the tree you get from a seed will not be true to it's mother and could look totlally differnt and it sometimes takes up to 4 years to really know whether it is just an ordinary looking tree or something worth keeping.David

Thanks David. If I did have seeds would they be near the leaves?

Yes you would see them amongst the leaves...they can be hard to see...as I said if you had that 10 day hard freeze after that warm early spring you probably won't have any this year hopefully next. I have had several 12-18 ft Atropurpureums amd Bloodgoods in the ground for 14 years and never noticed any seeds til last year( there were probably a few but I never noticed)... also a large 6+ft green "cut leaf" ( as they taged it) dissectum in the ground also about 14 years and only saw just a couple of seeds and that was last year also. David

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Here is a link that might be useful: picture of samaras