You haven't lost any rank. There are two different measurements you're confusing. [b]Vanguard Reputation:[/b] Vanguard Reputation is the number when you visit either your Vanguard Mentor in the tower (at the long table) or the Vanguard Vendor in the Ship Bay. It's displayed on the left side of the screen in a big circle. Hover over it and you'll see where you're at for "ranking" up. The higher reputation, you can access certain gear from that vendor. [b]Vanguard Marks: T[/b]he currency used to purchase gear from Vanguard Vendors. You get Marks from completing Public Events and playing in the Strike Playlist. [b]Where the confusion lies[/b]: you can only get a maximum of 100 Vanguard Marks per week. Every week on Tuesday, your "Marks Count" will reset to 0. This has no impact on the Marks you already have. Hit the options/Start button and tab to the right and you can see your current marks. This merely resets the counter. You're not losing rank, just misinformed :-)