Your assembly guide isn't lost. All our guides are free and online, so you can always get back to them.
You'll find them here: https://circuitmess.com/blogs/resources
Find your kit on that page and you'll get the full step-by-step build guide, and for most kits the usage guide and coding tutorials too.
All our projects are open-source, so the schematics, code and documentation are on our GitHub as well: https://github.com/CircuitMess
If you can't find the guide for your kit, email us at [email protected] and we'll send you a direct link.