SUMMARY krunner doesnt find some files, however baloosearch does. Of course the desktop search is enabled in the list of plugins of krunner. It seems the same bug that is reported here: https://bugs.kde.org/show_bug.cgi?id=388857 However Im using kubuntu 19.10 instead of a manjaro distribution.
*** This bug has been marked as a duplicate of bug 388857 ***
I solved this re-indexing everything, that is, disabling baloo, deleting the index file and re-enabling baloo.