We have to agree first what you consider as a common guitar piezo. If you disassemble it and analyze the mechanical design, you can determine if it can be expected to give considerable sensitivity in the 100 kHz range.
But I tend to agree with Frank. If the pickup is designed to perform cantilever vibrations, which gives maximum sensitivity at lower frequency, it's sensitivity at higher frequencies will be very low. For wideband sensitivity, longitudinal vibrations and a transducer with damping would be used.