Maybe their email is lastfirst@gmail.com, and people occasionally misremember your address and send your correspondence to them. In that case, yes.

More likely their email address is firstlastnumber@gmail.com or firstlast@otherprovider.com though, in which cases the types of mistakes people make are likely asymmetric.

periods are ignored in gmail addresses so there's no difference between firstlast@gmail.com and first.last@gmail.com