I do wish that Google would fix this. I like Chrome except for this problem which I have tried to overcome for a couple of years. I simply close my session like I always do with a bunch of pinned tabs. When I reopen it the tabs are all there and I can continue working; except when they don't. Occasionally I reopen Chrome and all my pinned tabs are gone. There was no crash so there is no alert to Restore. I open Chrome and see no tabs so I restore the previous session, but the previous session is the one in which I opened Chrome and found that there were no tabs.
I understand that Google is a fun, open place to work, but I wish they would put down the Foosball and fix this. It does not seem that hard to me that more than one previous session is available to Restore.
BTW, this most often occurs on my laptop when I have moved to a different network either at home or office, both recognized networks on my machine.