你的句子确实不妥。因为 until 后面通常不接现在分词，但若语境需要，可以接过去分词（可视为其前省略了主语和动词be）。如：

Leave in oven until cooked. 放在烤箱里一直到烤熟。

The soldiers marked time until ordered to advance. 士兵们原地踏步直至接到前进命令。

An accused man is presumed innocent until proved guilty. 被指控的人在被证明有罪之前应认为是无罪的。

Add four tablespoons of dried milk to a pint of cold water, and stir until dissolved. 在一品脱冷水中加入四汤匙奶粉，搅至溶解。

网友的句子可以考虑改为：

Being badly wounded and unable to move, he had to lie there until he got help.

Being badly wounded and unable to move, he had to lie there until help came.

Being badly wounded and unable to move, he had to lie there until (he was) helped.

我是这样看这个问题的：until用作介词，其后通常接时间，如：until tomorrow, until 10 pm，这是大家普遍熟悉和认可的。但语言是在不断发展的。实际上，特别是在表示和时间相关的语境，until接表示时间含义的短语在现代英语中已经很普遍，包括动名词结构，如until going to bed.在有些语境，我们通常也可以把until的这种用法理解为连词，后面省略相关主语。你的句子也可以这样理解，即until he was getting help。until going to bed 这种用法在英美报刊很常见，你可以去语料库搜一下。这种用法在非正式文体中有扩展的趋势，因此，你的句子在相应语境是可以接受的。我不知你的句子是在哪里看到的。当然如果是考试，应该避免为好。我给你几个外刊例句供参考：

此句可以理解为until they are starting to turn golden. until可以看作连词。

Being badly wounded and unable to move, he had to lie there until getting help. 由于伤势严重无法移动，在获得援助之前他不得不躺在那里。

网友以上句子可以改为以下几种句子进行表达

【1】Being badly wounded and unable to move, he had to lie there before getting help.【正确】

【备注:being badly wounded ...为现在分词作原因状语】

【2】Being badly wounded and unable to move, he had to lie there until he got help.【正确】

【备注:being badly wounded ...为现在分词作原因状语】

【3】Because he was badly wounded and unable to move, he had to lie there until he got help.【正确】

【备注:Because he was badly wounded ...为从句作原因状语】

【4】Because he was badly wounded and unable to move, he had to lie there until help arrived.【正确】

【备注:Because he was badly wounded ...为从句作原因状语】