katueu s/he hides it (anim) from someone tshikatuatin I hide it (anim) from you

Like VTA u-stems that alternate with a, an a surfaces in the inverse forms of these stems (e.g., tshikatuatin). However, this a doesn’t alternate with u, but is added after the stem (e.g., katu-). A verb like katueu has a u-stem that doesn’t alternate. For example, compare the homonyms petueu s/he brings her/him something and petueu s/he hears something

VTA u-Stems / VTA u-stems alternating with a
tshipetuatin I bring you something tshipetatin I hear you
nipetuakᵘ s/he brings me something nipetak s/he hears me
tshipetuakaunau we bring you (pl) something tshipetakaunau we hear you (pl)

VTA u-stems (non-alternating) belong to a category of verbs called Applicatives. They’re referred to as applicatives (or benefactives) because they are formed from a VAI+O to which a beneficiary is added to the action, i.e. the action is done for or to someone.

VAI+O / VTA Applicatives
petau s/he brings something petueu s/he brings something for her/him
katau s/he hides something katueu s/he hides something from/for her/him
pimutatau s/he sells something door to door pimutatueu s/he sells something door to door for her/him

See also Applicatives (Benefactives) and VTA u-stems (alternating with a)