my son TJ doesn't have alot of the features (the space between the toe, yes, almond eyes, yes) but he's a pretty long baby and most ppl can't tell he has ds. :) We know from an amnio.
My oldest son has DS and once diagnosed the doctors went down a laundry list of "physical features" that were present due to the DS. He looks just like his uncle - the wide space between his first and second toe, the almond shaped eyes, the long body and short legs. Just because a physical feature is associated with DS, doesn't mean DS always causes that feature. If you've done all the proper testing, it's pretty likely the child in question does not have DS.
yes it is possible and that is why before any diagnosis, any baby that is suspected of having DS needs to be genetically tested to confirm the diagnosis.