I also had an sizigium a year ago, looked exactly like the plant in the pics. The leaves of mine had quite an variation to their form, some were close to a surinam cherry leaf, others looked more elongated like the ones in your pics.
Cant tell what species of sizigium it may be, just can say it looks very close to the plant that i had, i thought mine was a surinam cherry , but the people here in the forum id it as a sizigium.