Full address was printed when you created register.
Since now we have logs for every command execution, you can find corresponding file and address for your register should be there.
safe register get b2ca21f75c6ecf090012f0fed5c2b67a6a254c4c7cac2906120b34b146433a258cedd286b7570ef14aaffd417a3759030a60079b9291c8dc0f0009c96337c9c17261d65cc258e07541d34a2b855e027c