Add third  parameter to wpsc_remove_item action, as it provides helpful context for the item being removed, context which is unavailable elsewhere.
Fix improperly interpolated variable in checkout fields.
Updated phpDoc block, avoid inspection warning

Return value was noted as voi instead of string.  Caused inspection warnings.
Check for thumbnail existence.  Not convinced this works, and even if it does, not convinced it's the best idea.
Resolve conflcits in 3eac29db163c2f35ab56908cf8499b2c41f1cfe1 for 3.8.14.2 branch