Great observations and speculations. All are possible reasons for the child to have cried. Sometimes they themselves don't even understand the real reason for being upset; they only know that they feel bad. Humans are definitely complicated creatures.

When my son was very little, he would constantly say the word, "pee" and I would need to take him to the bathroom because he was being weened out of diapers. It was very frustrating for me because most times he would not pee, but just wanted to flush the urinal or toilet. Eventually I figured out that he was fascinated by the fact water came out after tripping the lever! His lack of communication skills prevented him from telling me what he actually wanted, so instead, he used the one word he knew that would get him close to the real objective.