Grunter forgive me, I missed a session! Should I do it on my next off day?
Normally I would say that you just earned yourself a one-way ticket to Flogging Station 42, but this is an exception. The best thing for you to do is not stress about missing the (very) occasional workout. Instead, focus on hitting the next scheduled session. Life happens, and everyone misses a workout now and again. But cramming a training session into a rest day as penance will ultimately do more harm than good. Rest and recovery is when fitness gains are really made. If you have a lower-intensity session (say 80%) scheduled in the three days following a missed session then you can increase the intensity by 5%, since you’ll be coming at it a bit fresher.
As long as missing sessions doesn’t become a weekly habit you will still get plenty of training stimulus through these plans to give that Speed Demon of Sufferlandria a run for its furry money..