I was held up.

[keannu]

What do you mean by "held up" here? Stuck in traffic or somewhere? Can it be anything?

W: Don't tell me you forgot about the meeting.
M : Never, I was held up.

[5jj]

Only more context can tell us for sure.

[BobSmith]

Can it be anything?

not a teacher

Yes, though the implication is that, while M's tardiness was M's responsibilty, it was out of M's control (i.e. not M's fault). If not, M might have replied "I got lost." or "You told me the wrong time." or "I had something more important to do."