سَقَر has three letters, but the middle letter قَ is vowelled rather than silent. It therefore does not receive Hind’s optional treatment in the author’s classification.
In the constructed example تَحَدَّثْتُ عَنْ سَقَرَ (“I spoke about Saqar”), the name is genitive after a preposition but takes fatḥa as a diptote. This is a grammar example, not a scriptural quotation.