reckoner
Two different things decide a week here, and keeping them apart is what stops two weeks away from costing you a block.
The calendar decides when a week may turn. That happens on your own day one, at your own local midnight, and nothing you press makes it happen sooner or later.
A logged session decides whether it does. A week you were not in is a week with no evidence in it, so there is nothing to reckon: no lift progresses, no stall counter moves, and no lighter week is earned by sitting still.
What that means coming back
The week you left is the week that is waiting. Flu, a work trip, two weeks where it did not happen: none of them writes an empty week into your record, and none of them hands you a load you have not trained up to.
After a longer gap
A week or two away changes nothing. More than three weeks with nothing logged and your first week back comes in about 10 per cent lighter, and any lift that shows it had room to spare goes straight back to its old load rather than walking up to it. Past eight weeks away you start a new block with a calibration week, which measures where you are rather than guessing.