Here are the important parts of the timeline:
- You asked the question on Signal Processing.
- You got an answer there.
- You left the following comment on said answer:
- Peter K., a moderator on Signal Processing, migrated the question to ELU. (Whether this was due to your comment or something else only he can answer.) Nobody else on that site voted to close or migrate (otherwise their names would be listed).
- On ELU, the question attracted many comments, none of which were from the people who close voted. One person, however, said that it would be "better asked" on another site and suggested the math or physics site. In my opinion, the close reason "unclear what you're asking" can probably be taken at face value—anyone who hasn't seen an animation probably won't know what you're talking about.
- The question was closed on ELU, which rejected the migration, causing the ELU copy to be locked, and the Signal Processing one to be unlocked. A month later the question (again, on ELU) was deleted by Roomba because it was "more than 30 days old, and ... it was migrated from a different site, and then rejected". Unfortunately, because the question here is locked, only a moderator can do anything with it.
Hopefully the above explains what happened. The next obvious step in this case, since it looks like some terminology request questions have been well-received on Signal Processing (examples: 1, 2), is to see if it really is off-topic there (which seems to be exactly what you're doing). If not, then you can flag for a moderator here for it (and all the answers) to be unlocked and undeleted. At that point it could be edited and reopened by you and other regular users.