I've commented before on the difficult trade-off between the wonderfulness of an unusual surname (once you've found your guy, you know it's your guy) and the awfulness of an unusual surname (so very, very many ways to spell it incorrectly and then transcribe it some other way, making even soundex mostly useless). I had a couple of ideas, however, to find my Abbenhouses. One of them worked instantly: Cornelis Philip was living next door to his brother Henry in the 1910 census. Convenient. Also, explains why his brother's brother-in-law appeared on C Ph's wedding certificate as a witness: they were living together. I _still_ can't find any of them in 1920, and that's saying something, because the brothers had had all their kids by that point and the names weren't _that_ normal.
The next thing I went looking for was their mother, who immigrated to join her boys (leaving her adult, married daughter behind). Her immigration year was conveniently (albeit incorrectly) listed on the 1930 census, when she was living with my great-grandfather, so I knew I was looking for another single traveler in a passenger record (the brothers did not come over together). I had two possible last names, because I knew her birth name from genlias. But nothing I did in ancestry.com turned her up.
Before I gave up entirely in favor of an easier nut to crack, however, I said to myself, Self, you know perfectly well that other people have these records and they have their own indices and every index has its own problems. FamilySearch, obviously, but in this case, I headed over to www.ellisisland.org, where you can enter whatever you think you know. And lo, there was Jennie, complete with her daughter's address in the Netherlands and Henry's in Newport, Washington.
Easy, Peasy. When I browsed ancestry.com's ship's records, I realized that boat for that date isn't listed (even tho the Noordam is listed for other dates) -- this wasn't an indexing problem at all.
ETA: Another trip through the Gelders Archief turned up a birth record for the daughter left behind. Either it wasn't there the last time I looked or I missed it. Both are possible, since the provincial archives are entering records as an ongoing process. A lot of what is findable in the Gelders Archief is, similarly, not yet in genlias, which is a nation wide searchable database.
ETA: And FamilySearch has Janna's immigration record as the first hit on her name as well, however, if you want to view the image, you have to go to the Ellis Island site. So I would have wound up in the same place, regardless of where I started.