Yes, they are termites. I had them last year and I have already lost 2 bigguns to them this year. I just went out this morning to see the third leaning over. A quick dig down found them. i am also looking for a solution.
Yes, you can get them in containers if the container is in contact with the ground. Next time put a barrier that allows air to flow under the pot. That will stop them from rising into your soil.
My planted ones were left alone for two weeks, and then BAM!!! I guess everything loves weed....
Oh well.