Title Edit: Title of post changed from “Raft/Gyro Vanishing after sleep/save” to “Raft/Gyro Vanishing” as there are other factors involved.
Players may experience their raft has vanishing after sleeping or saving the game. The most common report of this issue occurring is when a player returns to their island (which may have an established base or large collection of items), leaves their raft and sleeps/saves immediately. Please see comments below regarding saving and checking the cartographer as this may also be a factor for a number of players.
Though rafts are more commonly reported, there is a chance that Gryos may also be affected, if you have lost a Gyro, please let me know below.
Unconfirmed: When returning to your island, especially if you have a significant number of items there or experienced lag on the way back, do not sleep/save immediately and if possible stay near your raft for a short while. The workaround for lag and crashing when saving - Staring at the sky for up to 5 mins to allow everything to catch up - may work in this situation.
Please see Reidz comments below regarding saving, checking the cartographer and then returning the game. If you raft disappeared under similar circumstances, please let me know below! Thank you. Link to comment: [Known Issue] Rafts/Gyro Vanishing - #8 by Reidz
SeanDon71 has shared what worked for them as a workaround below. Link to comment: [Known Issue] Rafts/Gyro Vanishing - #15 by SeanDon71
Please see Blankakong’s comment on their own post for what they tried with regards to checking the cartographer and the raft vanishing and what method they have found is safe for their raft. [PS4] Raft vanishing - #2 by Blankakong
xGnomeGrownx has included images below showing the way they store their raft to prevent it from being lost: [Known Issue] Rafts/Gyro Vanishing - #19 by xGnomeGrownx