Can't make rEFInd show boot menu again!
To get started, try to reset NVRAM:

Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R. 
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time.
Release the keys.

Resetting NVRAM

(If the rEFInd installation was performed  something like sudo bless --mount / Volumes / ESP --setBoot --file /Volumes/ESP/efi/refind/refind_x64.efi --shortform, and the boot volume information was recorded in NVRAM).