re: MISSING SIL IS BACK!!
^-- pray to Allah and read whatever part you want to read from the Quran but with khaloos and heart. i highly doubt the wazeefa to be read 70 or 200 times mentioned above can be found in any hadees.
I pray that sis-in-law returns home safe and sound as soon as possible inshAllah. May Allah swt keep her in his protection, Ameen. Let us know as soon as you hear any news :=)