Amazing! I grow Caryota mitis as an indoor plant, C. gigas 'Himalaya'
indoors and out depending upon the weather, Arenga engleri and
micrantha outside in the border and Wodyetia bifurcata indoors. All
of them have very similar shaped leaflets at certain ages and when
divorced from the plant are almost indistinguishable. There are a
fair number of other 'fishtail palms' with similar leaflets too
depending upon maturity. The pic is far too vague to make a call,
although it is fair to say that since C. mitis is the commonest,
there's a likelihood, but no certainty that the pic is of one of its
leaflets. Unless of course, the label is in the pot with the rest of
the plant that we did not see.