3" pitchers are probably not big enough to show the difference between N. alata and N. Ventrata. *Even on mature plants it can be difficult to tell. *Odds are it is not N. alata and highly likely it is N. Ventrata or N. ventricosa. *
A picture would help including a top down view of the leaves. *N. ventricosa the leaf blade gradually tapers all the way down until it connects to the stem. *N. alata has a very clearly seen petiole with none of the leaf blade extending from it. *N. Ventrata is somewhere in the middle with a little more taper of the leaf margin but still reaching the stem so the petiole is not clear. *There other things to look for but some may not be seen until the plant is quite large.
I would also agree that in many cases identifying an unknown Nepenthes is an educated guess at best and should always be labelled along the lines of this:
N. Ventrata -?
or N. Ventrata - identified as
Something to indicate that it's identity was unknown at one point. The last thing we need is to add to confusion.