Basement bathroom question

I have purchased a house that had a "rough in" Bathroom in the basement. It consists of an ejector pit, pump, drain for the sink and toilet and a 12''x10'' rectangle filled with gravel. I assume this is for a shower. The flange for the toilet is already there, there is no provisions for a drain for the shower installed. I tried digging out some gravel and found nothing. I only dug 3'' though. Does this setup sound familier to anyone? Thanks
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