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Usually first reward of the worthy came with a yellow transmutation geode. Today after the patch that wasn't the case. I didn't see a mention of this as a change in the patch notes.
This a change or a glitch?
To clarify, it's your first Rewards for the Worthy opened by any of your toons after the 20 hour cooldown from opening your last one. (At least I'm pretty sure it's 20 and not 24 - could be wrong.) It doesn't reset at a consistent time like daily writs and other repeatables.
You can take the Rewards coffers from your mail safely (although they don't stack), but looking inside one counts as "opening" it, so the contents are determined at that point even if you leave them in the coffer.
Are you sure that this was a coffer you hadn't opened (i.e. looked in) before and that it had been at least 20 hours since the last one you opened on any toon?