Good question -- I forgot about catalog numbers ...43 and ...44 until you mentioned them!
I think what happened was that when we planned Vidna Obmana's Opera For Four Fusion Works parts 1 through 4, we assigned hyp2239 as the catalog number to Act 1, and then subsequent catalog numbers were assigned to other planned upcoming releases, with 43 and 44 assigned to projects that either never happened (around that time we had planned to release a Mathias Grassow and Jim Cole disc that ended up being released on another label when the artists wanted the album released sooner rather than later), or that were assigned to different catalog numbers. My recollection was that hyp**43 and hyp**44 were set aside for the next two installments of Vidna Obmana's Opera, and that when those catalog numbers were kept the same as Act 1 (differentiated as hyp2239b, c and d since all four parts were really the same release) I probably forgot to recapture the numbers 43 and 44 and reassign them to new, upcoming projects as I would have normally done.
Speaking of catalog numbers, I don't remember if I've ever explained this before, but the catalog numbers work as follows. All Hypnos releases have a catalog number of hyp#### where the four-digit number has a last two digits that are assigned sequentially, and the first and second digits indicate the year of the release (first digit is the decade number, with 1 meaning "first decade" or 1990s and 2 meaning "second decade" or 2000s, with the second digit indicating the last digit of the calendar year. So, 16 = 1996, 19 = 1999, 21 = 2001, 28 = 2008, and 2009 will be 29 and 2010 will be 30. When the next Hypnos release comes out this year, it will be hyp2956 (since the last was hyp2855)