There was a pair of earphones on my desk just now.

问题补充：

There was a pair of earphones on my desk just now.的否定句无

答案：

There wasn a pair of earphones on my desk just now.

======以下答案可供参考======

供参考答案1:

就刚才我桌上还放着一副耳机。

供参考答案2:

刚才我桌面上有一个耳机。