Federal regs require every allegation to be reported and investigated. It seems your investigation revealed that no abuse happened. Tho a little difficult, any time I feel that a resident puts the employee at risk (with unfounded allegations or the risk for them) I simply require 2 staff members to be present when any care given or require the aide that doesn't gee haw to swap for another resident and stay out of that room- so far this has worked with the difficult residents.