If you use @Shadow on a field that starts with L with refmap remapping, the L will get dropped. This can be seen by depending on Create: Steam n' Rails in a development environment.

The issue is that MemberInfo.parse checks for semicolons before colons. LONG_CROSS key gets pulled out of the refmap (using Steam n' Rails as an example here) as LONG_CROSS:Lnet/minecraft/class_265;. So far so good. Then MemberInfo.parse sees that the value starts with an L and contains a semicolon. It decides that the owner is "ONG_CROSS:Lnet/minecraft/class_265" and the name is "". RemappingReferenceMapper then sees that the owner is non-null and the name is null. It then remaps the owner by itself, and converts the resulting MemberInfo to a string. This leaves us with a remapped name of ONG_CROSS:Lnet/minecraft/class_265. However, MemberInfo.parse (which is what invoked the remapping; AccessorInfo.inflectTarget -> TargetSelector.parseName -> TargetSelector.parse -> MemberInfo.parse) isn't done. It sees this remapped ONG_CROSS:Lnet/minecraft/class_265, finds no L or semicolon, splits it on :, leaving a descriptor of Lnet/minecraft/class_265 and a name of ONG_CROSS, drops the descriptor to get the name, leaving us with ONG_CROSS.

This can be fixed by moving the colon and left parenthesis checks before the semicolon check in MemberInfo.parse.