I found a couple of mentions in the Official Records:

Official Records of the Union and Confederate Navies ... ser.1:v.21. Page 106
Report of Captain Marchand, U. S. Navy, forwarding information obtained from deserters sent from Mississippi Sound. U. S. S. LACKAWANNA, Off Mobile, February 18, 1864
The other steamers in the bay are the Dick Keys, Magnolia, Natchez, and Virginia Pearl, which communicate between the forts and Mobile. The latter vessel is very old and worthless.

Abstract log of the C. S. S. Tennessee, Lieutenant James D. Johnston, C. S. Navy, commanding.
February 16, 1864.—Mobile River.
February 29.—The anchor was made fast at 8:25 a.m. and the Mary Virginia was made fast to our port quarter. At 8:35 the vessel got underway and steamed up the river. '' 9:25 a hawser was passed to the steamer Dick Keys from our starboard bow, which parted, and another was passed and she towed us down the river. At 12:45 came to with port anchor in 5 fathoms water and veered to 15 fathoms chain. Spanish River Battery bearing due south, distance 1 mile.

I agree with Dr. Russell that the Dick Keys was likely in the Mobile Bay or that vicinity on the date in question. The Moblie River and the Spanish River join just before entering Mobile Bay.