Complex sentence: Miller's inverted Jenny was stolen in 1977 but was recovered in the early 1980s, however that stolen and missing stamp served to drive the value of the other 99 examples even higher.
Split into simpler sentences: Miller's inverted Jenny was stolen in 1977 but was recovered in the early 1980s. However, that stolen and missing stamp served to drive the value of the other 99 examples even higher.