I assume this is a bug. But I have sticky traps an...

Sorry forgot to mention - Foliar spray!

1ml wood vinegar to 1 litre RO water - spray once weekly. This will not only keep critters away but will boost plant growth! Stop using once flowering.

I think your assumptions are correct in bugs. One other thing I would rule out is if anyone else has access to the tent and might have bumped it or more likely if you have a cat/pet and it went in for a little sniff n nibble as they love doing that. For the beetle, you could try treating the soil around the plant so if it goes into that area again it dies. Or another option is get a big yellow sticky trap, cut a slit to its center point and then wrap it around the trunk so the plants is cover in a little lake of yellow sticky flat against the soil line, Think of it like a bib or scarf aorund the trunk also commnly called a "tree skirt" but this phrase is more for christmas shit but same idea. This way if the beetle comes back up to feed it will have to walk across the trap/skirt to get to the plant and it will hold it. This is assuming it does not eat the roots instead. Also can water the plants or move em to much when the skirt is in place or it will not be sticky anymore. Good Luck!

Caterpillar??