Revenue Ruling 90-38, which is an IRS version of the debate on how many angels can dance on the head of a pin, says:

A taxpayer may not, without the Commissioner's consent, retroactively change from an erroneous to a permissible method of accounting by filing amended returns, even if the period for amending the return for the first year in which the erroneous method was used has not expired.

https://bradfordtaxinstitute.com/Endnotes/Rev_Rul_90-38.pdf 

Have you asked the taxpayer and/or his previous preparer, why no depreciation was claimed?  Maybe the entire value of the property was in the land -- it would be worth more with the building torn down.