Lost history after rename of test column

Running Hobbit 4.2.0. After rename of some custom tests and deleting the old name, discovered that trying to view History tells me "cannot open history file". It appears there is no history file for the newly named tests, that I can find. Neither is there one for the old named tests, which is probably due to my having deleted the test column.

I know there was history for the old named test.

Have I missed a step? Do I need to run rrdtool, create, or something?