Your heart sinks. You need to change the database credentials. You need to remove the backlink in the footer. You need to debug a fatal error. But you can't. It’s locked.
If you provide these details, I can point you toward the most reliable recovery methods currently available. free free ioncube decoder
If you are a business that has lost its own source code, hire a reputable code restoration firm. They are expensive, but they operate legally and provide clean, working code. Conclusion Your heart sinks