Hamlet Defnese Chests

[zzapp]

Please let me apologize in advance for such a noob question. I would sincerely appreciate clarification on how the hamlet defense chest works. I have done this a number of times, good scores, bad scores, failures. As best I can recall, at the end, I've always clicked on a chest, similar to Ifrit or Moogle run, but yesterday, by the time I got there, the chest was gone. Both runs I got absolutely nothing, no DM, etc. Prior to yesterday, as best I can recall, I've always had a chest to click on. How does this work?
Someone told me if I'm not near the chest when it's opened I cannot get any drops. Is that true also? Thanks.

P.S. - I didn't even get any DM yesterday with the chest gone.