The record among the stones

The burial-ground map I had been given was thirty years old. It numbered the memorials by row, but several new stones had since been inserted and two older ones had been moved beside the boundary wall. Some inscriptions were so worn that I could distinguish individual letters but not always a whole name. Ivy covered dates near the bases, and the rules prevented me from removing any growth without the groundskeeper's permission. The paths were narrow, and I could not reach the backs of stones in the central rows without stepping over graves, which I would not do. The final index had to record each inscription in full and link it to its present location, without counting the same memorial twice.

Describe how the conditions could make the final index incomplete or inaccurate. You may support your points with brief quotations.