How to find DB created in SQLite

I'm using this code to load the data from DB ontime into the data frame in R.

library(RSQLite)
library(DBI)

ontime <- dbConnect(RSQLite::SQLite(), dbname = "ontime.sqlite3")
from_db <- function(sql) {
  dbGetQuery(ontime, sql)
}

from_db("select count(*), tailnum from ontime group by tailnum")

tails <- from_db("select distinct tailnum from ontime")

However, it seems that R cannot find DB ontime that I created from SQLite shell.

Error in sqliteSendQuery(con, statement, bind.data) : 
  error in statement: no such table: ontime

I tried to search ontime on disk, but I didn't find it. I also double-checked that this DB exists by using select * from ontime command. So, where is this DB stored on disk and how can I find it?