Slightly-but-not-completely-dumb question

[R_D]

So I did a quick search but couldn't find anything after about 10 minutes of looking (sorry if I did happen to miss it--in that case sue me).

Forenote: I was playing on "Adventure" mode.
Basically while playing my first character (a halfling archer), I got a grey vial as a drop from the first boss. I figured out I could Identify it, so I did so. It ended up being something called "Blood of Life" iirc. It said it let me revive from death once. I thought to myself "Nice! An extra life!" That's all fine and dandy. (as a further identifier to try and ensure I'm not remembering the item wrong, it had a sell price of 50 gold) I died 3 times in the 2nd dungeon, but each time the Eidolon revived me. I knew I didn't have many revives left, if any, but I succeeded in conquering the dungeon. After leaving, I roamed the map and found myself in this frozen waste area and got prompted to enter a trapdoor where I heard someone calling for help. I choose to do so, and conquered a short thief/assassin dungeon and rescued this merchant. (I only mention this to give some indication of my level as that affects the amount of times the Eidolon will res you, and I don't remember for certain what my level was--I always attempted to make sure I killed every enemy, barring ones you would fight by triggering summoning traps; screw summoning traps lol)

Now I decided to try and track down the tooth of a sandworm for an alchemist quest, so I went to the far west of the map where I saw this hole in the beach while exploring, and entered it. Sure enough, it was a sandworm lair. That is all fine and dandy as well. Here comes the clincher though--I thoroughly cleared the first floor, then went to the second. There I found myself fighting some level 25 translucent (grey?) slimes (the rest of the enemies here were approximately levels 8-12). Like 10 of buggers. They killed me, and the Eidolon revived me again. I killed/escaped from the rest of the slimes, and continued further. I found a chest, opened it, and inside was a rare classed lvl 11 mass of worms that started spamming multiply. Long story short, I died again. I was faced with a new menu this time--the Eidolon apparently had grown tired of rescuing me, but I wasn't phased--I could use my blood of life right...? ...right?

I couldn't use it. I don't know why, but I was given no prompt to use it--I could only restart from same character, restart from new character, save character to dump file to remember it or something, and exit to main menu. What gives? Did I do something wrong? Did I have to use the blood just before I died? Or did it bug? Please help me, because while that character is long gone (I've since overwritten it), I'd like to know if I did something wrong so if the situation arises again I don't make the same mistake or if I was just the victim of an unfortunate bug.

[omeg]

You need to use the Blood of Life, it basically grants one extra life after that.

[R_D]

You need to use the Blood of Life, it basically grants one extra life after that.

Ah, so I needed to actually use it as soon as I got it? Well, that's... unfortunate. Thanks very much for the info though, that's what I needed to know!