Castr records livestreams in the cloud for the last 4 hours. If your events are only 30 minutes each and you stream twice a week then we will be having data for the last two streams of 30 mins in our cloud.
You can toggle "Enable DVR" option in stream settings page on top your embed url field.
Once DVR is enabled your will be able see all previous streams in your player embeds.
You can also check the recorded contents under VOD Episodes section in stream settings page.