Did you note from which side of the engine the oil had dripped based on its position on the cardboard? It doesn't necessary mean that you still have a leak, could be oil from the old leak that dropped on the subframe.
I would probably give it a good shot from below with anti-grease (what is the correct word in English?), then take it to a washer with a good underneeth cleaning. Then keep an eye on the oil level and if you continue to have leakage. Small drops can be considered normal for an engine of this age but any substantial leakage needs to be taken care of. Also pay attention as much as possible to from where you get the oil drips, that will help diagnose it.
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