well obviously there were 2 pendants, seeing as how marle had one at the same time as schala, so there isnt really a plot hole
there is only one pendant. the pendants are from different times in its existence in the same time because of the time traveling.
the plot hole had to do with changing slightly what happened to schala which made her pendant end up with kid not eventually making its way to marle or somethine like that
In a sense, there are 2 pendants;
#1 In the FMV where Lucca sees the baby with Schala's pendant
#2 Marle still has her pendant, even though we don't see her wearing it at the wedding scene
Kid has the pendant Schala sent down with her, that is fact. However, on the Zenan mainland, Marle still has her pendant, if she did not die when Porre attacked Guardia. My question... Schala's pendant originally made its way to Marle in the original timeline, before the telepod was used. What happended to Schala? In the new timeline created by Crono and co. Schala sends Crono's party out of the Ocean Palace and vanishes along with her pendant that would soon be sent along with the clone of herself, the clone being created somehow with the struggle of Lavos.
This just hit me though... what if it was the other Schala from the original timeline before Crono ever interfered? Kid = Schala, yes, but hear me out. What if both Schala's combined there powers to send one other outside of Lavos's restraint? It was a success, but it left one of the Schala's DNA being re-written, their genes altered, and having been reverted back to a mere baby. Is anyone following me here or did I loose some people?
I am saying that the original Schala was either the one who reverted into the baby, becoming Kid, or the one you freed from the TD. When the CC was used, both Schala's may have become one, yet retaining the knowledge of the other as well. This can be confirmed by Kid's quote at the very end of CC before the credits roll.
Ideas?