You can use /ping list to see who sent you pings and you sent pings to in the last seven days. If you have turned off ping DMs, this command comes in handy to see who has tried to reach you.
In addition to seeing your recent pings, you can also verify that you are actually able to receive ping messages from the bot. Simply click the button at the bottom to test.
Pings will be deleted from Vibrant after seven days to retain the sender's and the recipient's privacy. However, when pings are deleted, this does not remove direct messages sent to users by the bot.