Home inspectors are generally not liable to discover defects that are concealed from view. Also, mold may not within the scope of a home inspection.
Either way, evidence water or moisture damage should be a sign that mold problems may be possible. Many buyers learn the hard way that a deficient home inspection could fail to reveal mold contamination.
Especially these days with mold being a problem in foreclosed homes, not discovering mold infestation before the purchase of a home can lead to costly expenses. Competent home inspectors should notify potential buyers of a possible issue, and perhaps recommend a professional mold inspection be performed.