Where is user theme stored?

[pgr]

you can disable the SuitePImproved theme globally in config_override.php

Re-enable Theme

disabling themes can be done in config.php with something like this: 'disabled_themes' => 'SuiteP,Suite7', And in config_override.php something like this: $sugar_config['disabled_themes'] = 'SuiteP,Suite7'; So your change probably created one of those entries (or both), you can go there and un-do them manually.