No, that´s not normal but it will happen if you have un-checked "Generate waveforms automatically during import" in Preferences > Audio. I assumed that you had Premiere Pro closed when you deleted the files.
IMHO it´s better to go select the clip/s with no audio waveforms and then go to Clip > Generate Audio Waveform to get them back.
Thank you (and Merry Christmas!) Just as an experiment, I deleted some, and when I put the video back in the timeline, the waveforms didn't show up, and the program didn't indicate it was generating .pek files. Is that normal?
By @roberth63696283
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