To know what the last transaction log backup of your database was, execute the T-SQL script below.
SELECT
CONVERT(CHAR(100), SERVERPROPERTY('Servername')) AS ServerName,
msdb.dbo.backupset.database_name AS DatabaseName,
MAX(msdb.dbo.backupset.backup_finish_date) AS Last_TLog_Backup_Date
FROM msdb.dbo.backupmediafamily
INNER JOIN msdb.dbo.backupset ON msdb.dbo.backupmediafamily.media_set_id = msdb.dbo.backupset.media_set_id
WHERE msdb..backupset.type = 'L'
GROUP BY
msdb.dbo.backupset.database_name
ORDER BY
msdb.dbo.backupset.database_name
