F.5E, F.5F, clearing reset, document could not be found

Today I have been trying to find out why in F.5F log I see warning messages with text “Document not found”.
After little investigation it has become clear that document could not be found if it is created via batch input, which is prepared by F.5E run for items which could not be posted online. There is also a clue in the bottom of F.5F log. It tells us to check whether a batch input SAPF180/ has been created.
One example of why documents could not be posted online is reseting of a clearing that relates to some blocked previous period. The fact is that in this case posting is done to that previous period. And because it is blocked the posting could not be completed. So it goes to batch input. Conclusion: don’t forget to check SM35 in case of warnings or errors in F.5F log!
By the way: when we performed batch input for such clearing resets we simple changed the posting date to the current period.
Open question: why is posting date of clearing reset choosen as a last date of the period which the resetted clearing relates to?