The lomoco package lists six sources, one of which is pool/main/l/lomoco/lomoco_1.0.0-1.debian.tar.gz which leads to a 404. This feels like something which ought to be reported to someone, but whom?
Welcome to the forum! 
You’ve posted this in the AUR category, but there is no locomo package in the AUR. There is however a package called openloco, of which the description reads… 
An open source re-implementation of Chris Sawyer’s Locomotion
Is this the package you are referring to? If so, then you can probably file a bug report at the project’s GitHub page.
On the other hand, your thread title refers to lomoco, which is indeed an AUR package, but not quite the same thing as locomo. 
In that case, the reference for the package points at the Ubuntu Launchpad, which in turn lists the Debian QA Team as the package maintainers. So I’m guessing you’ll need to take it to the latter. 
There was, but it was deleted sometime before October 2022.
That’s probably why.