New plant sprouting from clone?

Hey guys, my buddy recently purchased 4 clones. Today he checked on them and found a sprouting weed plant! I confirmed it was a weed plant. I asked if it had a seed shell anywhere next to the seedling and there was not. Is it possible that a new plant can sprout off of the roots? I have seen this one other time on here and everyone was baffled by it. I told him to remove it from the soil gently and replant it and he has done so. My question is, is it possible for a weed plant to sprout off of the roots? Or did the guy who sold the clones accidentally drop a seed into the soil?

The seedling that emerged looked like this.

It has cotyledons so I would think it had to come from a seed.

Skuxx said:

It has cotyledons so I would think it had to come from a seed.

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Here is a pic from him, this is after removing it from the cup with the clone

A dropped seed sounds like the only explanation. Good advice on getting it into a pot on its own.

Looks like a seed starting to me as always thank you for your time and the best wishes

Johiem said:

A dropped seed sounds like the only explanation. Good advice on getting it into a pot on its own.

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That’s what I figured. He was just saying no seed shell in sight, and it wasn’t there yesterday lol I told him hopefully he got lucky with an exotic seed!