Why would you assume that this was in development in 2006? Touchscreen technology wasn't nearly as seriously being pursued, let alone 'make it one tenth of a millimeter thinner' touchscreen technology, at that point.
While it's possible Apple had this brilliant insight into the possibility of the future, but I am reduced to two possibilities.
1) They had their own technical people knowledgeable enough to know about the potential and create it independently of known research out there.
2) Some research division/company had this in development but was wavering about its potential, apple saw it and went and filed the patent themselves.
Both are very unlikely in my view. Perhaps you have another scenario?