If JndiLookup.class is removed, and somebody attempts to trigger the exploit, what happens?

One of the possible mitigations for the recent vulnerabilities is 
removing the JndiLookup.class file from the log4j-core jar.

One thing I am wondering is what happens if that step is taken and 
somebody manages to cause an application to send the exploit text to the 
log?  Down in the bowels of log4j code, I think a ClassNotFoundException 
will be thrown ... what does that exception mean for log4j as a whole? 
Is it handled gracefully?

I'm with the Solr project.  Solr switched to log4j2 in the 7.4.0 
version, and at that time, it was 2.11.0 that was included.  My hope is 
that the API has remained stable enough from 2.11.0 through 2.16.0 that 
simply replacing the log4j jars is a safe operation.  We have had users 
claim success when doing that replacement on their Solr installs, as far 
back as log4j 2.13.0.

Any information you can provide is appreciated.

Thanks,
Shawn