Your residence permit was issued based on §28 (1)(1) AufenthG.
- Spouse of a German citizen that resides in Germany
If you and your German spouse no longer reside in Germany, then the residence permit expires automatically, since the conditions it was issued against are no longer fullfilled.
Only if your spouse remained in Germany and/or you applied for an exception of the 6 month rule before leaving (need 12 months to take care of parents), would the residence permit had remained valid.
Once this condition is again fulfilled, a new residence permit will be issued.
You should contact the local German embassy / consulate, which will probably issue a D-Visa based on §28 (1)(1) AufenthG.
Section 28 AufenthG
Subsequent immigration of dependants to join a German national
- (1) The temporary residence permit shall be granted to the foreign
- spouse of a German,
- minor, unmarried child of a German,
- parent of a minor, unmarried German for the purpose of care and custody
if the German’s habitual residence is in the federal territory.