Hi, @hbuckle,
Thanks for posting about this. Here's an explanation I posted in an older thread about how this could happen: Ocsp server responses for new certificates - #2 by JamesLE
In this case, we did have replication lag during the few minutes when your certificate was issued. I've opened a retroactive incident status report showing the timeframe: Let's Encrypt Status
Sorry about the trouble! We monitor and alert on replication lag, and will keep working on ways to prevent it from affecting OCSP.
It's reasonable for you to expect that a new certificate will immediately have a valid OCSP response available; and, it's also best practice to make sure that your ACME client and integrations will gracefully handle cases when that fails.