I've been struggling all day with a complex sheet, discovering multiple times throughout the day that formula's appear to have been deleted.
Before Filtering - every cell had a value, either 0.000 or greater; parent rows were totalling correctly.
Action:
Filter column 'Q1 Total' to show only those cells that had a value (as a result of a formula in the cell (=[Q1 Lic Rev]70 + [Q1 NRE]70 + [Q1 ReSW]70 + [Q1 Mtce]70)); when I did not get the desired result I 'Removed All Filters'.
Result:
- formulas are deleted (the cell is now blank) when; cells had a Q1 value; as well as the SUM(Children()) formulas for the parent cells (where a child had a Q1 value)
It appears formula's and data elsewhere in the sheet may have been deleted as well, however will not know for certain until I rebuild the missing data 
- formulas are intact: for cells that were $0 (as a result of the formula in that cell) the formula is intact.
This has resulted in hours and hours of rework today and a company wide blast to NOT USE FILTERING
Please advise if I need to open a trouble ticket.