Station Stones 92 and 94 do not have pages because the stones are missing. Their positions are indicated on the ground by modern stone and steel markers, one on the South "Barrow" and the other on the North "Barrow".
Four sarsen stones that might be expected to complete the sarsen circle are also missing (eg Stones 13, 17, 18 and 20) and so those stones do not have pages either. Evidence that the sarsen circle was intended to be complete arose during the dry summer of 2013 when a series of parch marks appeared in the circuit exactly where some of the missing uprights should be.
See: Simon Banton, Mark Bowden, Tim Daw, Damian Grady and Sharon Soutar (2014). Parchmarks at Stonehenge, July 2013. Antiquity, 88, pp 733-739. doi:10.1017/S0003598X00050651.