Is he considered an innovator who commits or orders an innovation—such as reciting Surat Az-Zalzalah ten times to bring back an absent person—while ignorant of the rulings and acting based on his own ijtihad (independent reasoning)?

A distinction must be made between an act being an innovation (bid'ah) and judging the perpetrator of that act as an innovator (mubtadi'). An act might be an innovation, but its doer is not labeled an innovator due to an excuse or an interpretation. Not everyone who falls into an innovation becomes an innovator, but whoever persists in it after clarification is an innovator. The specific warning associated with innovation only applies to those against whom proof has been established. Regarding the recitation of Surat Az-Zalzalah a specific number of times with the intention of bringing back a missing person, this has no basis and falls under innovations, for acts of worship are prescriptive.