Thank God you saw the crack before it went into the warmer!! This is why I posted about buying better buckets a few months ago.
5 Gallon Buckets
I am finding that 5 gallon buckets used to store honey are only lasting me a couple of seasons. I buy them primarily from box stores (Lowes/Home Depot) and from Tractor Supply. The upper lips seem too thin and will crack after a few lids have been malleted on and pried off for a few seasons...