It looks rather privet-ish to me as well, but I've had a quick look through my old but trusty houseplant book - maybe Hoya (wax plant) or Solanum (winter cherry)? Has it ever had flowers or berries? That would help with an ID.
A tip for growing ‘foraged’ seeds is to take a photo of the plant and the seed and make a little folder of them with numbering then you can stick a label in the pot and number it the same … that’ll give you and us a start when it’s time to ID it. 😊
“I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh
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Ficus benjamina has alternate leaves...which rules it out.
what did the plant the seed came from look like.