In BIble Search (NA27) I was searching for greek:ημερα, but the results did not include Matt 28:15 where ημερα occurs in brackets [].
ημερα by itself performs a manuscript search (surface:ημερα), so it won't find Matt 28:15.The [ ] are coincidental!
If you wish a lemma search, use Morph Search. When you accept the suggestion for ημερα it will change the search to lemma:ημερα. You can then select Bible Search, which transforms it to the more complex <lemma = lbs/el/ἡμέρα>, and then search.
Silly me... of course, you are right. I was misled by the fact that it found the dative singular (with iota sub) and jumped to the wrong conclusion.
