Sorry to hear what happened.
It's interesting that he was at a conference, presumably speaking about what he always speaks about.
This means his bag and things were to advance his mission, which is kind of to advance a 'commons'.
it nicely illustrate's RMS's philosophy (gpl). Even though he was speaking to advance the public good, a private enterprizer took his bag, removing it from the commons he worked so hard to advance.
RMS's philosophy, code, and bags require the protection of law.