I assume it was a Grantor (Living) Trust?

Since your client did not know about it, Mr. Smith may have added your client's name "for convenience". Then your client gets dod FMV as basis.

On the other hand, if Mr. Smith intended to make a gift to your client, more info is needed.

How was it titled? Joint w/ right of survivorship? Tenants in common? Transfer on death? How much of the property was included in Mr. Smith's estate? What was shown on the Probate filings? Your client's basis may be Mr. Smith's basis, or it may be a portion of Mr. Smith's basis and a portion of the dod value.