A note from Little Moonbeam's father

, is a note Sydney's father left her when he was dying in the Statesman Hotel. If you give it to her after she tells you her story, she will give you Sydney's 10mm "Ultra" SMG.

Location
The "note" can be found on the third and uppermost floor of Statesman Hotel Mid Level, close to the center. Just south of the marker for the Statesman Hotel Restaurant elevator (but behind a wall, so not directly accessible).

If you are making your way up to Reilly's Rangers for the first time, it is two floors above Theo. The room is the first door to the left (facing north looking down the corridor immediately after leaving the stairwell to that upper floor). The door is opposite a locked door, which is a storage closet (easy difficulty) with ammo and med supplies. Just beyond the storage closet is a side-by-side fire hose and med station on the wall. Once you enter the hotel room, just look for the illuminated bedroom. The note is on a bed, next to a skeleton, under the ceiling light.

Transcription
Весточка от отца Лунного Лучика

Workaround
If you already completed the Stealing Independence quest without meeting Sydney, she may disappear. You can make her reappear using the console commands.

She will appear in the rotunda of The National Archives, but she won't offer any interesting dialogue. If you don't want to kill her, you can reset the Stealing Independence quest:

If you've already been here and killed the Super Mutants of the rotunda, she will still be stuck waiting for them.

Now, talk to her to get her joining you, then, complete the quest using the following command:

Sydney will then head to Underworld, you will be able to barter with her and to get all the dialogues of the A note from Little Moonbeam's Father quest.

Note: If you type instead of the, you may get the dialogues too, but she will continue to follow you. This may make the game unstable.