Studio lost my changes

I was doing a demo and around 4:58PM EST today (May 7th 2019), part of what I built was lost:

• Project targuillere-SANDBOX, empty project (applied my "empty-10.10" tag before the demo)
• I created a Contract document type with 2 fiels (owner, User/Group, and internal_ref, String)
• Then an Event Handler (ContractCreated), for event Document Created, type Contract. I chose to dynamically create the ContractCreated automation chain
• This chain just Document.SetProperty the contract:internal_ref field
• Went back to summarize what I did: Displayed the Contract and its field, Displayed the event handler, displayed the automation
• Then, back to the Contract I clicked the "Configure layouts in Designer" button

 
Then, the mess started:

• It opened designer, but no layout was displayed. Left menu items were there. The "Local layouts" arrow was expanded but nothing in there
• I refreshed the page => Same, no local layout
• I went back to Modeler and could see that:
•         -> The Contract document was removed
•         -> The ContractCreated event handler was removed
•         -> (ContractCreated automation was stil there)

I had to redo everything but the automation chain: Recreate the contract and its field, re create the event handler, then back to the contract I the button to create the layouts brought me to Designer, but slicing "Generate missing layouts" created only the Create and Edit, not the other ones.
I created the manually (click "configure") for each of them)

For info, I am in "Intermediate" mode.