You could create an alert off of the following out of the box search which looks for VM with recent config file (VMX) changes
vm.config.dateModified:[now-7days TO *]
This should return VMs with config changes in the last 7 days in this case.
You could also use the "Compare" (DNA) feature to then drill in and see what changed.
This doesn't seem to solve it because vMotions apparently touch the file and affect the Modified date.
You might have to use a vCenter alarm. "VM Reconfigured" might be the right Event but I haven't tested it.