Found him in Oregon in 1890 Vet Schedule listed as a Confederate "Surgeon, no unit given", Wife Frances is listed as well.

Name: Alvin L Cobb
Gender: Male
Role: Veteran
Residence Date: Jun 1890
Home in 1890 (Township, County, State): Island City, Union, Oregon
Enumeration District: 74
Rank: Surgeon
Company: View image
Regiment or vessel: View image
Length of service: View image
Household:
Name Role
Alvin L Cobb Veteran